Thanks, the BoundTo property does work, but there are new problems coming up. The DisplayValue of the combobox gets empty when the control gets the focus,

This is a known issue with combo boxes in grids when the RowSourceType of the combo box is either 2-Alias or 6-Fields. Using any other RowSOurceType fixes the problem.

and the lengh of the display value is limited to the lengh of the bound field.

Also a known issue and documented in the knowledge base:

PRB: DisplayValue of ComboBox is Truncated in a GridPSS ID Number: Q156771

Symptoms
When a ComboBox is placed in a grid, the DisplayValue of the ComboBox appears truncated.

Cause
The DisplayValue is longer than the field to which the column is bound.

Workaround
Set the InputMask property of the Column to the length needed for the DisplayValue.

Status
This behavior is by design.