Hi Leon,
This is just your Query Part. You will be filling your ComboBox using something like this:
oCombo.ValidValues.Add(Value1, Value1Desc);
So while using this method to fill the ComboBox at the very first time, you can use:
oCombo.ValidValues.Add('', '');
This will add one null value in the ComboBox.
You need to use this line to select the Null Value:
oCombo.Select('',BoSearchKey.psk_Value)
Else you put your code here. So that we can have a look.
Hope it helps.
Thanks & Regards
Ankit Chauhan
SAP Business One Global Support