i posted this is a different forum section and didn't get any answers at all, so i'm hoping someone here can help me out.

ill try to explain what im looking for
lets say i have a value in A1, lets say its 100, and if i have B1 set to percentage and enter 100% C1 would return 200, so C1 would have "=A1*(1+B1)"
but, my question is, is it somehow possible to enter the value of C1 manually and have B2 return the increase in percentage "=(C1-A1)/A1"
and have both formulas working at the same time so i can decide which one i want calculated by entering the value in the other one.