I have the following problem.

On top of cell B20 like in B15 there is a pivot table.
My problem is that in cell B20 I have a formula that uses the value from
B15, but every time the pivot table changes, the value I need is no longer on
B15 but in B17 or B13 depending if there is more or less data in the pivot
table.

How can I still use the value from B15 in order to keep my formula in B20
intact?

Thanks to all.