Private Sub ComboBox1_Change()
If Me.ComboBox1.Value = "" Then Exit Sub
Dim i As Long
For i = 2 To Sheets(Me.ComboBox1.Value).Range("A" & Rows.Count).End(xlUp).Row
Me.ComboBox2.AddItem
Me.ComboBox2.List(Me.ComboBox2.ListCount - 1, 0) = Sheets(Me.ComboBox1.Value).Range("A" & i)
Me.ComboBox2.List(Me.ComboBox2.ListCount - 1, 1) = Sheets(Me.ComboBox1.Value).Range("B" & i)
Next
End Sub