Combobox selection in datagridview

Question

Hi,
I am using vs2005 and desgining a windows form which had datagridview on it. The datagridview contains three columns. One combobox and two textboxes. But when i select the combobox or textbox for edit, i need to click twice. For rg. on first click the combo box is selected and on second click it opens with dropdown. How to select and open it on single mouse click.

Thanks