I finally got this to work! I now have a grid that will give the user a visual cue that there is a choice to make in a combobox, or that he has no choice (either zero or just one value is available).

Within the grid, the same column will display a combobox with the drop-arrow if the user has a choice to make, and a textbox if there is zero or just one value available. The key is that you must use an array as the RowSourceType of the combobox, prefill the array with all possible combobox values for all rows of the grid, then use the FirstElement and NumberOfElements properties to control just what is displayed in the combobox dropdown for each grid row.

That in combination with DynamicCurrentControl to control whether the combobox or the textbox is displayed, and Column.Sparse = .F. so that the drop-arrow will display in more than one grid row where appropriate.

Sergey and Marcia, thank you for all your suggestions!

-Curt