Here is a useful piece of code to set the ComboBox dropdown height for VB6 ComboBox control.
Dim oldscalemode As Integer
' This procedure does not work with frames: you cannot set the ScaleMode to vbPixels, because
' the frame does not have a ScaleMode Property.
' To get round this, you could set the parent control to be the form while you run this procedure.
If TypeOf oComboBox.Parent Is Frame Then Exit Sub
' Change the ScaleMode on the parent to Pixels.
oldscalemode = oComboBox.Parent.ScaleMode
oComboBox.Parent.ScaleMode = vbPixels
' Resize the combo box window.
MoveWindow oComboBox.hwnd, oComboBox.Left, oComboBox.Top, oComboBox.Width, lNewHeight, 1
' Replace the old ScaleMode
oComboBox.Parent.ScaleMode = oldscalemode
I've found this code on the web.
I would like to thanks to the original developer :-)