>In that case, how about this workaround: have a special string, say "(null)" in the combo for where we should have real nulls, then when saving, if there's this string in the field that's cbo's controlsource, replace that string with a real null.
>
>How bout that?

I've added setting NullDisplay to 'NULL' in lAddBlank_assign method and added the following code in the Valid event of the combobox that seems to solve the problem (I would need more tests tomorrow):

if this.listindex > 0
	if this.rowsourcetype = 5 and isnull(this.aRowSource[this.ListIndex,2]) ;
			and this.boundcolumn = 2 and not empty(this.controlsource)
		replace (justext(this.controlsource)) with null in (juststem(this.controlsource))
	endif
endif