Civil 3d Design check for summit curves

[sb208918]

Well hello everybody..I 've been trying to develop this design check criteria for a very long time which accounts the grade change for curves.As it is well know that sight distance at least equal to stopping sight distance should be provieded at all points on highway for summit curves. Two cases are to be considered in deciding the length..

Case I: L>SSD where,

                            L= NS^2/4.4 and                              

Case II: L<SSD, where

                            L=2S-4.4/N.

( L=Length of summit curve N=Grade change, S=Stopping Sight Distance)

I tried this:

IF({Profile Curve Length}>40,{Profile Curve Length}>=(16*{Grade Change})/4.4,(80-960/ABS({Grade Change})))

where S=40

but its not working. Is there an end to this ? Can this be done ? I am literally pulling my hairs out at the moment....any suggestions will be highly appriciated. Thank you..