OK, here is what I did:
1. Right click the DataGrid in question.
2. From the pop-up menu, select 'Properties'.
3. From the 'Property Pages' box, select the tab 'Format'.
4. In the 'Format Item' drop down, select the column you wish to format.
5. In 'Format Type', select Boolean.
6. For 'True Value', type 'Yes'.
7. For 'False Value', type 'No'.
I left the 'Null Value' blank because this field in my DB, Inactive_Physicians, is formatted to 'Yes/No' and I believe defaults to 'No'. Double check your DB field to see how it is formatted in case the blank value for NULL throw's an error in your code.
Anyway, that's from memory so if it doesn't work for you let me know and I'll go back thru the actual project.
Bubarooni