How to check if the player is in a certain area?

So I'm trying to figure out how to check if a player is in a specific area in the map, but I don't know what method to use. Basically I want it so while the player is in an area a value is set in their player to true. This would then communicate with other scripts to make an effect.

This is pretty simple. You can use Region3.new() . That is one method. You can put a Part in the area that you want the player to be in. Region3

This is the script

local part = -- Put the part path here.
local value = -- Put the value name here(In a string, else it will not work), Has to be in the player and not in one of the children of the player
function CreateRegion3(Part)
	return Region3.new(Part.Position-(Part.Size/2), Part.Position+(Part.Size/2))
end

function FindPlayerInRegion3FromPart(PartToFindPlayerIn)
	local partForRegion = CreateRegion3(PartToFindPlayerIn)
	local playersInRegion3 = workspace:FindPartsInRegion3(partForRegion, nil, math.huge)
	
	for i, v in pairs(playersInRegion3) do
		local player = game.Players:GetPlayerFromCharacter(v.Parent)
		if player ~= nil then
			if player:FindFirstChild(value) then
				player[value].Value = true
			end
		end
		return player
	end
end

while wait(0.5) do
	FindPlayerInRegion3FromPart(PartToFindPlayerIn)
end

If this does not work, please comment and I will try to fix it. After this you can do the communicating with scripts for the effect.