Para agregar items al ComboBox desde excel puedes intentar hacer esto:
Código:
Private Ex As New Excel.Application
Sub rellenar()
For i = 0 To 6
Combo1.AddItem Ex.Cells(12 + i, 2), i
Next
End Sub
Private Sub Command1_Click()
rellenar
End Sub
Private Sub Form_Load()
Ex.Visible = False
Workbooks.Open "ruta.xls"
Workbooks(1).Sheets(1).Select
End Sub