This is the UDF

Function ROll2D6()
ROll2D6 = Application.RoundUp(Rnd() * 6, 0) + Application.RoundUp(Rnd()
* 6, 0)
End Function

At current, when Excel recalculates, the random number generated by this
function, is replaced by another rnadom nuber.

Is there some sort of check that I can put into the UDF whereby IF the
current value of the cell (calling the function) is a number, it will return
that number instead of a new one.?

Thanks