This began as a work-related project, making use of a fixed-width font for simplicity. The author still has no real background in the weird and wacky world of Windows programming, but this example provides an interesting (albeit non-standard) demonstration. (Dialogue boxes appear to be the proper way to do these things...)
Ordnance Survey provide a number of free products, including map tile graphics and postcodes with northing & easting values. (Okay, so this project does have graphics files associated with it, but it's the exception to the general rule!)
The graphics and postcodes in this example have been pre-processed, so are not how Ordnance Survey provided them.
Combo (drop-down) box
TIFF image display (see the BB4W Wiki entry)
Child window, using R.Russell's handy MultiWin functions
Download a 50Mb zipped folder containing everything here.
Just for fun...
The following image was generated by plotting the density of postcodes i.e. all the northing & easting values provided by Ordnance Survey: