Private Sub UserForm_Initialize()
ComboBox1.List = Application.Transpose(Range(Cells(1, 1), _
Cells(1, Rows(1).Find("*", , , , , xlPrevious).Column)))
End Sub
Private Sub ComboBox1_Click()
ComboBox2.Clear
ComboBox2.List = Cells(2, ComboBox1.ListIndex + 1).Resize _
(Cells(Rows.Count, ComboBox1.ListIndex + 1).End(xlUp).Row).Value
End Sub