Can't change value stored in workspace. What I do wrong?

Hey. I stuck and I completely don't know why it doesn't work.

local foriStringVar = packLoc..".available"
local cheChange=false
print(foriStringVar)
f.getInstance(foriStringVar).Value=cheChange

I want to change BoolValue.Value to false. So I convert the string with its location to the instance and change it. But the value doesn't change from true to false.

PLEASE HALP! prob as always I do some stupid error