A Combo box can be dropped down when its focus is set, which would ease the selection of an item while making data entry. For this you have to call SendMessage API from the GotFocus event of the Combo box.

'**Include the following lines in the declaration part

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Long, lParam As Any) As Long

Const CB_SHOWDROPDOWN = &H14F
Const NUL = &O0

'Include the following lines in the GotFocus event of the Combo box
Dim lReturnVal as long
lReturnVal = SendMessage(Combo1.hwnd, CB_SHOWDROPDOWN, -1, NUL)