Activating the formula

Thanks but what i want is to activat a cell' formula (in my case a function which interpolate from a two set of data for a particular value (from a other cell) which is again has circular reference with the cell having the formula.

Problem is that after opening the worksheet the iteration doesn't start, upon activating (formula bar f2 and entering) the cell with the function interpolate , the iteration starts and give the correct value.
next time when i open the same woork sheet, the value lost.

If you can help me. sending u the excel file where col c has to activated to get the result. can it give result without activating each cell (here the cell in col C)

Regards

Raj