hi,
you already have the formula
if cost = e16 and gm = f17 then formula in e17 would be
=e16/(1-f17)
the other formula would be much the same except using the % instead of a
cell reference.
in g17, =e16/(1-.15)
in h17, =e16/(1-.2)
in i17, =e16.(1-.25)
ect, ect
regards
FSt1