Opening a form from a combobox

[GregJG]

I have a form with a combobox (cboCust).

If "add a new" (which is in the list of cboCust) is selected, or if the text typed into cbocust is not located in the list of cbocust, I want it to automatically open up another form (newcustfrm). the newcustfrm needs to open when the user leaves cbocust.

I have been using a simular vba code in worksheet_change to do it with a certain cell on a worksheet. but I would like to be able to do it from a form. This is what I am using on the worksheet;

Private Sub Worksheet_Change(ByVal Target As Range)
Dim found As Range
With Target(1)
    If Not Intersect(.Cells, Range("D3")) Is Nothing Then
        If Not IsEmpty(.Value) Then
            Application.ScreenUpdating = False
            With Workbooks.Open("f:\db1.xls")
                Set found = .Sheets("Cust").Columns(1).find( _
                What:=Target(1).Value)
                .Close True
            End With
            If found Is Nothing Then frmNewCust.Show
        End If
    End If
    Application.ScreenUpdating = True
End With

I have been trying to code this into cboCust_change() but can't seem to get anything going.

Can anyone help?