ComboBox

Hy anyone,
I´ve found problems about the ComboBox, in my application I need to
use the arrows (directionals) to select a command, the problem starts that,
when the dialog with ComboBox is shown I can´t use the arrows, first of
all
I need to use the mouse to select a item and after that I can use the
arrows,
I don´t know what it´s happening… after that I need that item can be
selected
pressing Enter, I´m incapable to do this anyway.
I´ll be very pleasure if you can help me.

Thanks a lot

Paulista