Private Sub butFind_Click()

Dim p As Integer

With Me!mNettoText
    .SetFocus
    p = InStr(.SelStart + .SelLength +  1 , .Value, Me!txtFind.Value)
    If p >  0  Then
        .SelStart = p -  1 
        .SelLength = Len(Me!txtFind.Value)
    Else
        Beep
    End If
End With

End Sub

Dim gSelStart As Integer, gSelLength As Integer

Private Sub mNettoText_GotFocus()
Me!mNettoText.SelStart = gSelStart
Me!mNettoText.SelLength = gSelLength
End Sub

Private Sub mNettoText_LostFocus()
gSelStart = Me!mNettoText.SelStart
gSelLength = Me!mNettoText.SelLength
End Sub

Private Sub Form_Current()
gSelStart =  0 
gSelLength =  0 
...
End Sub