Found the original thread here.
https://www.ozgrid.com/forum/forum/h...aining-formula

I'm having the same problem as the OP had right now. Unfortunately, I have no idea what is VBA and how it works at all. I want to use the codes they used but I don't know what to edit or how to even activate it.

In my case, I have a couple of sheets. They contain some cells I have to allow user to enter the value manually, or leave them blank then formula comes back again.

This is Sheet1
=IFERROR(AVERAGE(D17*F17),"")

This is Sheet2
=IFERROR(AutoTaxInvoice!D17,"") *AutoTaxInvoice!D17 contains texts, don't know if this information necessary.

Thanks.