You mean, set the dropdown width of the combobox?

Change the Public to Private if you want to use in the form declarations.

Code:
Public Declare Function SendMessage Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, ByVal wParam As Long, _
lParam As Long) As Long

Public Const CB_SETDROPPEDWIDTH = &H160

Public Sub SetComboWidth(oComboBox As ComboBox, _
lWidth As Long)

' lWidth is in pixels

SendMessage oComboBox.hwnd, CB_SETDROPPEDWIDTH, lWidth, 0

End Sub