Label Printing Help

I am trying to create a simple app that will print barcode labels based on a range entered by a user.

The problem i have is that with the following code the label values are all the same:

Code:

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Dim SA As SECURITY_ATTRIBUTES
        Dim hPortP As IntPtr
        Dim poStart As Integer = txtStart.Text
        Dim poEnd As Integer = txtEnd.Text
        Dim i As Integer = poStart

        objhPort = CreateFile(objLPTPORT, objGENERIC_WRITE, _
                        objFILE_SHARE_WRITE, SA, objOPEN_EXISTING, 0, 0)

        hPortP = New IntPtr(objhPort)
        outFile = New FileStream(hPortP, FileAccess.Write, False)

        fileWriter = New StreamWriter(outFile)

        fileWriter.WriteLine("N")


        Do Until i = poEnd + 1

            fileWriter.Write("A120,30,0,a,1,1,N,")
            fileWriter.Write(Chr(34))
            fileWriter.Write("*PO" & i & "*")
            fileWriter.Write(Chr(34))
            fileWriter.Write(Chr(13))
            fileWriter.Write(Chr(10))
            i = i + 1
            fileWriter.WriteLine("P1")
            fileWriter.Flush()
        Loop

        fileWriter.Close()
        outFile.Close()
        retval = CloseHandle(objhPort)

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If i add all the code within the the loop, the label values are correct but it prints out slow because the printer prints out a label sets itself then prints the next one.

Im using a Thermal printer so speed of the printing is key.

Thanks for any help.