>Can I use combo box in grid like I can use checkbox? I've been trying to do so, but my combo does not work.

Yes, put the grid in edit mode, select the combobox control and click on the column you want to drop it in (click the header to select the column, then click in the textbox area of the column). You know it works when the combobox button on the control library bar raises back up. Make sure you make the combobx the CurrentControl of that column.