cursor invisible when I set the DroppedDown = true for a combobox.

Question

Hi All,

My project is a VSTO ( VS for Office ) and I have created a new control to enter some user data similar to Excel's formula bar.
The UI has a RichText box and when user type a chr I populate a combo box with valid values start with the chr user typed in ( auto complete).

The issue is, when I set the droppedDown = true for the combo, the cursor is getting invisible. the control is listed in Excel and when i move the mouse towards the bottom, it becomes visible. when I move the mouse to excel's area the cursor become invisible.

If I don't set the droppeddown = true, user need to click on the combo and in that case no issues. but I am trying to remove the extra click.

Does anyone face this proble? any idea how to fix this? thanks for the help.