I'm using Excel 2000. In a particular file only, when I enter a UDF as a
formula, and the dialog showing the parameters is displayed, I see that the
function will produce a correct, non-zero result. When I click OK to save
the formula, 0 is displayed.

When I try adding a breakpoint to the first line of code in the UDF, it is
never reached.

I then enter a formula into another cell, it can be anything including the
same UDF as used in the first cell. This time when I click OK, the
breakpoint in the UDF is reached (twice when this 2nd cell uses the same UDF
as the original formula), and then I see the correct results displayed in
both of the cells.

If I then edit the original formula again (and not change anything), it
again does not braeak at the beginning of the function, and shows 0. Edit
the 2nd cell, and both will then display correctly.

The value does not recompute when I change the cell values that are used for
the UDF parameters either, even though I have the calculation set to
automatic.

It's very strange. What could be causing this?

Thanks!