Mike,
Just out of curiosity I tried the following code with a combo box and nothing changed.
rcall SendMessage,hCombo,CB_SETEXTENDEDUI,TRUE,0
Add string like this.
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 1"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 2"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 3"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 4"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 5"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 6"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 7"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 8"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 9"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 10"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 11"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 12"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 13"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 14"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 15"
rcall SendMessage,hCombo,CB_ADDSTRING,0,"String 16"