Creating a .bmp file with Put statement

I am trying to craete a bmp file programatically. (It is for a GIS style application in excel where I can make full use of the colour pallate and use a very large grid. I've explored charting options and shape objects but they have limitation. This will be a much better solution).

Here some of my test code to create a bmp. I cribbed it from an example and changed some of the header parameters and the pixels to try and craete a picture with random dots. It kind of works in that it doesnt crash and creates a file with all the correct bytes in as far as I can tell (I read them back in and compare them with another bmp).

When I actually open the file it is just black with dimensions 1392x1040 pixels. Not what I've specified.

Any suggestion on what I'm getting wrong?

Here's the code.

Sub BMP_Gen()
    Sheets("Sheet1").Select
    Dim bmpHeader As bmp8
    With bmpHeader.bmiHeader
        .biSize = Len(bmpHeader.bmiHeader)
        .biWidth = 1392 ' pixel width of bitmap
        .biHeight = 1040 ' pixel height of bitmap
        .biPlanes = 1
        .biBitCount = 8 ' 8 bits per pixel
        .biCompression = 0 ' not compressed
        .biSizeImage = .biWidth * .biHeight
        .biXPelsPerMeter = Int(72& * 1000 / 25.4)
        .biYPelsPerMeter = .biXPelsPerMeter
        .biClrUsed = 0 ' all colours may be used
        .biClrImportant = 0 ' all colours are important
    End With
    With bmpHeader.fileHeader
        .bfType = &H4D42
    End With
    Dim m As Long, h As Long, v As Long, vIn As Long
    
    Open "c:\tmp5.bmp" For Binary As 1
        vIn = Cells(1, 6)
        Put 1, , vIn
        For m = 2 To 68
            h = Cells(m, 5)
            v = Cells(m, 6)
            Put 1, h + 1, v
        Next m
    Close 1
    Dim b1() As Byte
    Open "c:\tmp5.bmp" For Binary As 1
        ReDim b1(0 To LOF(1) - 1)
        Get 1, 1, b1()
    Close 1

    Dim n As Long
    Dim Txt As String
    For n = 0 To UBound(b1)
        UserForm1.List1.AddItem Format(n) & vbTab & Format(b1(n))
        Txt = Txt & Format(n) & vbTab & Format(b1(n)) & vbLf
        Cells(n + 1, 8) = Format(n)
        Cells(n + 1, 9) = Format(b1(n))
    Next n

End Sub

The attachment may help for debugging purposes -- it reads bmp headers, and will plot the picture and the RGB values (within the limits of Excel 2003's 256 columns) for uncompressed bmps with 24-bit color.

Please don't look closely at the code -- it's oooold.