Hello,

In my project I create user-defined functions in Excel. Some of them do I/O
operations that are not always available. In such case a user-defined
function returns #INVALID value to the result cell.

My question: If there is previously calculated value in the result cell, is
it possible to restore it in case my functions are not able to return a
value at a time? Is there some API or technique that can be used?

I understand that there could be certain complications - for example in case
the UDF is part of a formula.

Thank you for your time!

Nacho