How to make this keep going when you hold down the left mouse button?

It's a chainsaw script, and I'm trying to make it keep going while you're holding down the left mouse button.

r = game:service("RunService")


local damage = 10


local slash_damage = 25

sword = script.Parent.Handle
Tool = script.Parent

Slashing = false

local SlashSound = Instance.new("Sound")
SlashSound.SoundId = "http://www.roblox.com/asset/?id=2766576"
SlashSound.Parent = sword
SlashSound.Volume = 1
SlashSound.Pitch = 1

function blow(hit)
    if (hit.Parent == nil) then return end -- happens when bullet hits sword

    local humanoid = hit.Parent:findFirstChild("Zombie")
    local vCharacter = Tool.Parent
    local vPlayer = game.Players:playerFromCharacter(vCharacter)
    local hum = vCharacter:findFirstChild("Humanoid") -- non-nil if tool held by a character
    if humanoid~=nil and humanoid ~= hum and hum ~= nil then
        -- final check, make sure sword is in-hand
        local right_arm = vCharacter:FindFirstChild("Right Arm")
        if (right_arm ~= nil) then
            local joint = right_arm:FindFirstChild("RightGrip")
            if (joint ~= nil and (joint.Part0 == sword or joint.Part1 == sword)) then
                tagHumanoid(humanoid, vPlayer)
                if Slashing == false then
                    Slashing = true
                    if hit.Name == "Head" or hit.Name == "Torso" then
                        print'CARNAGE!'
                        humanoid:TakeDamage(damage)
                        Tool.Blade.Hit:Play()
                        if hit.Parent:FindFirstChild("Torso") then
                            hit.Parent.Torso.RotVelocity = hit.Parent.Torso.RotVelocity + Vector3.new(math.random(-30,30),math.random(-30,30),math.random(-30,30))
                        end
                        Tool.Bloodeh.Bloodieh.Enabled = true
                        untagHumanoid(humanoid)
                        wait(.1)
                        Slashing = false
                    elseif hit.Name == "Left Arm" or hit.Name == "Right Arm" or hit.Name == "Left Leg" or hit.Name == "Right Leg" then
                        print'Limb-Taking!'
                        humanoid:TakeDamage(damage * .8)
                        Tool.Blade.Hit:Play()
                        if hit.Parent:FindFirstChild("Torso") then
                            hit.Parent.Torso.RotVelocity = hit.Parent.Torso.RotVelocity + Vector3.new(math.random(-15,15),math.random(-15,15),math.random(-15,15))
                        end
                        Tool.Bloodeh.Bloodieh.Enabled = true
                        untagHumanoid(humanoid)
                        wait(.1)
                        Slashing = false
                    else
                        print'ARMORED...'
                        humanoid:TakeDamage(damage * .2)
                        Tool.Blade.Hit:Play()
                        if hit.Parent:FindFirstChild("Torso") then
                            hit.Parent.Torso.RotVelocity = hit.Parent.Torso.RotVelocity + Vector3.new(math.random(-5,5),math.random(-5,5),math.random(-5,5))
                        end
                        Tool.Bloodeh.Bloodieh.Enabled = true
                        Tool.Bloodeh.Materialleh.Enabled = true
                        untagHumanoid(humanoid)
                        wait(.1)
                        Slashing = false
                    end
                end
            end
        end
    elseif humanoid == nil and hum ~= nil then
        if hit.Transparency ~= 1 and hit.CanCollide ~= false then
            Tool.Bloodeh.OtherMaterialleh.Enabled = true
            Tool.Bloodeh.Materialleh.Enabled = true
        end
    end
end


function tagHumanoid(humanoid, player)
    local creator_tag = Instance.new("ObjectValue")
    creator_tag.Value = player
    creator_tag.Name = "creator"
    creator_tag.Parent = humanoid
end

function untagHumanoid(humanoid)
    if humanoid ~= nil then
        local tag = humanoid:findFirstChild("creator")
        if tag ~= nil then
            tag.Parent = nil
        end
    end
end


function attack()
    damage = slash_damage
    SlashSound:play()
    Slash()
end

function Slash()
    Tool.GripForward = Vector3.new(-1,0.2,0)
    Tool.GripPos = Vector3.new(0,0.1,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.4,0)
    Tool.GripPos = Vector3.new(0,0.2,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.5,0)
    Tool.GripPos = Vector3.new(0,0.3,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.8,0)
    Tool.GripPos = Vector3.new(0,0.4,0)
    wait()
    Tool.GripForward = Vector3.new(-1,1,0)
    Tool.GripPos = Vector3.new(0,0.5,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.8,0)
    Tool.GripPos = Vector3.new(0,0.4,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.6,0)
    Tool.GripPos = Vector3.new(0,0.3,0)
    wait()
    Tool.GripForward = Vector3.new(-1,0.4,0)
    Tool.GripPos = Vector3.new(0,0.2,0)
    wait()  
    Tool.GripForward = Vector3.new(-1,0.2,0)
    Tool.GripPos = Vector3.new(0,0.1,0)
    wait()  
    Tool.GripForward = Vector3.new(-1,0.0,0)
    Tool.GripPos = Vector3.new(0,0,0)
    wait()
end

Tool.Enabled = true
local last_attack = 0
function onActivated()

    if not Tool.Enabled then
        return
    end

    Tool.Enabled = false

    local character = Tool.Parent;
    local humanoid = character.Humanoid
    if humanoid == nil then
        print("Humanoid not found")
        return 
    end

    attack()

    wait(.1)

    Tool.Enabled = true
end


function onEquipped()
    sword.Start:Play()
    sword.Idle:Play()
end

function onUnequipped()
    sword.Idle:Stop()
end

function stopTouching(hit)
    if (hit.Parent == nil) then return end
    local humanoid = hit.Parent:findFirstChild("Zombie")
    if humanoid~=nil then   
        if hit.Name == "Head" or hit.Name == "Torso" or hit.Name == "Left Arm" or hit.Name == "Right Arm" or hit.Name == "Left Leg" or hit.Name == "Right Leg" then
            wait(.5)
            Tool.Bloodeh.Bloodieh.Enabled = false
        else
            wait(.5)
            Tool.Bloodeh.Bloodieh.Enabled = false
            Tool.Bloodeh.Materialleh.Enabled = false
        end
    else
        if hit.Transparency ~= 1 and hit.CanCollide ~= false then
            Tool.Bloodeh.OtherMaterialleh.Enabled = false
            Tool.Bloodeh.Materialleh.Enabled = false
        end
    end
end


script.Parent.Activated:connect(onActivated)
script.Parent.Equipped:connect(onEquipped)
script.Parent.Unequipped:connect(onUnequipped)


connection = Tool.Blade.Touched:connect(blow)
Tool.Blade.TouchEnded:connect(stopTouching)