Private Sub Workbook_Open()
Dim vMonths As Variant
Dim vYears As Variant
Dim i As Integer
'Create date arrays
vMonths = Array("Jan", "Feb", "Mar", "Apr", "May", "Jun", _
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec")
vYears = Array(2006, 2007)
'Populate months using AddItem method
For i = LBound(vMonths) To UBound(vMonths)
Sheet1.ComboBox1.AddItem vMonths(i)
Next i
'Populate years using List property
Sheet1.ComboBox2.List = WorksheetFunction.Transpose(vYears)
End Sub