insert record(vb.net 2003)

Private Sub AddEntry()
        Dim cnSQL = New OleDbConnection(con)
        Try
            cnSQL.Open()

strSQL = "insert into tblbilling(InvoiceNo,[Sold to],Address,tin,date,itemid,description,quantity,unit,unitprice,total,Gross,vat,[total invoice]) Values('" & txtInvoiceNo.Text & "','" & txtsold.Text & "','" & txtaddress.Text & "','" & txttin.Text & "','" & txtdate.Text & "' ,'" & txtItemID.Text & "' ,'" & txtparticulars.Text & "'," & txtquantity.Text & ",'" & txtunit.Text & "'," & txtunitcost.Text & "," & txtTa.Text & "," & txtgsp.Text & "," & txtvat.Text & "," & txttia.Text & ")"
            Dim cmSQL As New OleDbCommand(strSQL, cnSQL)
            cmSQL.ExecuteNonQuery()

Dim strSQL1 As String = "insert into tempBilling(InvoiceNo,[Sold to],Address,tin,date,itemid,description,quantity,unit,unitprice,total,Gross,vat,[total invoice]) Values('" & txtInvoiceNo.Text & "','" & txtsold.Text & "','" & txtaddress.Text & "','" & txttin.Text & "','" & txtdate.Text & "' ,'" & txtItemID.Text & "' ,'" & txtparticulars.Text & "'," & txtquantity.Text & ",'" & txtunit.Text & "'," & txtunitcost.Text & "," & txtTa.Text & "," & txtgsp.Text & "," & txtvat.Text & "," & txttia.Text & ")"

Dim cmSQL1 As New OleDbCommand(strSQL1, cnSQL)
cmSQL1.ExecuteNonQuery()
cmSQL1.Dispose()
cnSQL.Close()

 Catch Exp As OleDbException
MsgBox(Exp.Message, MsgBoxStyle.Critical, "SQL Error") ''
Catch Exp As Exception
MsgBox(Exp.Message, MsgBoxStyle.Critical, "General Error")
End Try
End Sub