attachment

[adil_karampurwa]

in my application send mail, on click of a button "Attachments" we can attach any file but if we dont attach any file
error is thrown.
error is invalid use of null
code for it is
Private Sub cmdAttachment_Click()
Dim intReturn As Integer, strarray() As String
If IsNull(txtAttachment) Then
txtAttachment = ahtCommonFileOpenSave(, "C:\", , , "pdf", _
, "Select file to attach")
Else
txtAttachment = txtAttachment & "; " & ahtCommonFileOpenSave(, "C:\", , _
, "pdf", , "Select file to attach")
End If
intReturn = SplitVB5(txtAttachment, "/", strarray)
strDisplayName = strarray(intReturn)
intReturn = SplitVB5(strDisplayName, ".", strarray)
strDisplayName = strarray(2)
txtAttachment.Visible = True
lblAttachment.Visible = True
cmdAttachment.Caption = "Add Another"

End Sub
plz help me