Do you mean you want to show the DatePicker when you click the combo arrow?
I think you'd be better off building a textbox/button combination control
that "looks" like a combo, and then calling your datepicker in the Click
event of the button ... you can set the Left/Top properties of the
datepicker to line up with the textbox, and the user will never be the
wiser!!
To get the down arrow symbol on a button, change the font to WingDings (or
one of the variants) and find a character that does what you want. You can
use the Character Map (on my XP box it's at Start - Programs - Accessoreis -
System) to review the various characters.