Thanks John, I ended up finding something i can use on another site. It wasn't what i originally wanted but it will do.
Private Sub Cbocontract_AfterUpdate()
Me.CboMth1.RowSourceType = "Value list"
M1 = Format(DateAdd("m", -5, Date), "MMMYY")
M2 = Format(DateAdd("m", -4, Date), "MMMYY")
M3 =...