Someone help me with this script?Any Ideas? Chat commands does not work as intended.[UNANSWERED]

Here is the script:

if string.sub(message,1,7) == "health/" then
local number = nil
for i = 8,math.huge do
    if message:sub(i,i) == "/" then
        number = i
        break
    end
    end
    local plr = FindPlayer(message:sub(8,number-1))
    local amt = message:sub(number+1)
    print(plr.Name.."/"..amt)
    end
    end

I tried this

--I chatted this:
"health/pl/8"
--it print this
>Player1/8
--then i tried this
"health//999"
---it print this
>Player1/999
--How do you make it so that when you say this: "health/pla/999"
>Player1/999
---and if you say this: health/NoPlayerThatExist/999
--it will print nothing and not Player1/999

Thanks!!!