My Excel is 2003 SP3.

I have a Combo in a Form with MatchRequired false (because I want to customize the error message).

There is a 2 columns range whose name is stored in RowSource property.

Blank is a valid choice, so I have included a empty line in that range.

First column ( BoundColumn=1 Linked to Value default property) indicates the final return.

Second column ( TextColumn=2 Linked to Text property) is what I see in the form (WidthColumn="0 pt")

When I choice the empty value in the Combo, the Excel correctly set value property to "".
However, when I set the value to "" before show it, Excel puts the null value,

Why? How to I can circumvent it?