ExcelBanter

I have a formula with circular reference. When a I put any valur in
any of these reference cells the formaula gets overwritten by the
value. Is there any way that I can put values in any of these cells
without overwriting the formuls to try various permutations. Below is
the example:-

Cell A B C
500 10 2%
Formula +C1*A1 B1/A1

Cell B1 & C1 are having formula with cicular reference. What I am
trying to get is that if I change the B1 value to 50 from 10, then C1
should automatically change to 10% & vice versa. OR If C1 is changed
to 10% B1 should change to 50 so that I can try as many combinationas
possible.

The problem here is that once i put "50" in B1 or "10%" in C1 the
formula gets overwritten with the absolute value.

Would be thank ful if anybody can suggest any solution for this?

Regards
Abhi