Can't Get A Combobox To Show The Value I Want

i searched for similar combobox features, nut didn't find any that helped.

i have 2 unbound combos that get heir values from different tables

first combo1 gets its values from a query
SELECT [tbl_music].[MID], [tbl_music].[Artist], [tbl_music].[Song], [tbl_music].[CID] FROM tbl_music;

combo2 gets values from
SELECT [tbl_category].[CID], [tbl_category].[Category] FROM tbl_category;

IDs are autonumber and primary
The CID fields in the tables are in a 1..* relationship

Both are constructed with the wizard and the ID columns are hidden.

What i need is:
when selecting something from combo1, the combo 2 should show the right category for that song.

Hope i explained clearly enough.
I tried to use the dlookup function, but i get error 94, invalid use of null.
i'm using the afterupdate event.

I can update a textbox text, but can't do so with the combobox value.

Any ideas what i'm donig wrong :confused: :confused: :confused: