.OnAction method when enter pressed

Hi,

I have a commandbarcombobox (edit control) which is to function as a searchbox. I want a method to be called when the user presses the enter key in this combobox. I tried assigning a method name to the .OnAction property of the combo control but it never gets called ( no errors either).
Is there any other way for me to capture the enter key press event. The combo only has an on change event and it fires event when I click in the combobox with a mouse and then click outside anywhere else on the command bar ( and I don't want my search to be triggered randomly like that)

Any suggestions would be most welcome.
Thanks,
Juhi.