Hi Dag,
If you are finding that process intensive perhaps your device is not appropriate for your needs. I don't know what device you are using.
Are you using AXF data or shp files? Perhaps with AXF you can use SQL statements to update the table which might be quicker.
For example have 1 table with everything in it. Have a duplicate table, but completely empty. Attach this to your combo box. When you make the change call a SQL command to update the empty table attached.
Let me know how you go.
Cheers,
Gareth