I am making a spreadsheet to calculate centerline developed length. You are
given either the INSIDE RAD/LENGTHS or OUTSIDE RAD/LENGTHS. If you get the
inside, you add, if you get the outside, you subtract...both getting the same
result. I want to be able to have the cell that displays the centerline
dimension to use both ways though. If I only enter the outside dims and leave
the inside dims blank, I still want it to show the centerline values.
Hopefully this is clear enough for someone to help me out.

Thanks!