alternative to the previous solution.
still on combo's AfterUpdate Event:
private sub combo_afterupdate
if me.combo.listindex > -1 then
docmd.applyfilter , "[code unik] = '" & me.combo & "'"
' if the visible value on combo is not the bound column:
'docmd.applyfilter , "[code unik] = '" & me.combo.Column(1) & "'"
else
' remove the filter
docmd.showallrecords
end if
end sub