Edit box displays a list of identical letters

[Kevin]

for starters this line in wrong

case EN_CHANGE<<16|4 sub.OnTextChanged lParam
its a ComboBox not  an edit control
that line does nothing. The event never fires!

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case CBN_EDITCHANGE<<16|4

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but using this
    case CBN_EDITCHANGE<<16|4 sub.OnTextChanged lParam
the drop box will fire below the combobox.
Not sure why you want a combobox and then want to create another dropdown box