first version
"create" your combo-box in your ressource-file, for example in a
dialogwindow with
"COMBOBOX id, x, y, width, height, [style, [extended-style]]"
default-style is CBS_SIMPLE | WS_TABSTOP
second version
create a combo-box-window with CreateWindow(....) with classname "COMBOBOX".
To control your ComboBox use the Window-messages beginning with CB_....,
for example: an application sends a CB_GETCOUNT message to retrieve the
number ob items in the list box of a combo box.