Option Explicit
Private Sub Command1_Click()
Dim i As Long
For i = 1 To 10
Combo1.AddItem i \ 2
Next
End Sub
Private Sub Command2_Click()
Dim i As Long
For i = 1 To 10
If check_cf(Combo2, i \ 2) = False Then
Combo2.AddItem CStr(i \ 2)
End If
Next
End Sub
Function check_cf(obj, txt)
Dim i As Long
check_cf = False
For i = 0 To obj.ListCount
If CStr(txt) = obj.List(i) Then
check_cf = True
Exit For
End If
Next
End Function