mail merge - Object reference not set to an instance of an object.

[honeypot]

An unhandled exception of type 'System.NullReferenceException' occurred in PostBook Planning Dept.exe

Additional information: Object reference not set to an instance of an object.

The above error occurs when trying to run mail merge in my program. My code is as follows:


Private Sub InsertLines(ByVal LineNum As Integer)
Dim iCount As Integer
Dim wrdApp As Word.Application
Dim wrdDoc As Word._Document
' Insert "LineNum" blank lines.
For iCount = 1 To LineNum
wrdApp.Selection.TypeParagraph()
Next iCount
End Sub

Private Sub FillRow(ByVal Doc As Word.Document, ByVal Row As Integer, _
ByVal Text1 As String, ByVal Text2 As String, _
ByVal Text3 As String, ByVal Text4 As String)

With Doc.Tables.Item(1)
' Insert the data in the specific cell.
.Cell(Row, 1).Range.InsertAfter(Text1)
.Cell(Row, 2).Range.InsertAfter(Text2)
.Cell(Row, 3).Range.InsertAfter(Text3)
.Cell(Row, 4).Range.InsertAfter(Text4)
End With
End Sub

Private Sub CreateMailMergeDataFile()
Dim wrdDataDoc As Word._Document
Dim iCount As Integer
Dim wrdApp As Word.Application
Dim wrdDoc As Word._Document
' Create a data source at C:\DataDoc.doc containing the field data.
wrdDoc.MailMerge.CreateDataSource(Name:="C:\DataDoc.doc", _
HeaderRecord:="Name, Address_1, Address_2, Address_3")
' Open the file to insert data.
wrdDataDoc = wrdApp.Documents.Open("C:\DataDoc.doc")
For iCount = 1 To 2
wrdDataDoc.Tables.Item(1).Rows.Add()
Next iCount
' Fill in the data.
FillRow(wrdDataDoc, 2, "", "", _
"", "")
FillRow(wrdDataDoc, 3, "", "", _
"", "")
FillRow(wrdDataDoc, 4, "", "", _
"", "")
' Save and close the file.
wrdDataDoc.Save()
wrdDataDoc.Close(False)
End Sub

Any ideas on why this error occurs???