After the user has pressed button in the mapform, the following standard windows interface will open.
The user needs now to navigate to the proper directory and load a shapefile. If it is a polygon shapefile, it will be loaded and automatically zoomed to full extend in the map window. Please note, that only one shape file can be selected at a time. If you load a new shape file, the previous one will be unloaded.
Automatically, a new window will pop up, asking the user to determine a code field and a name field out of the attribute fields of the selected shape file. This is done by selecting first a field and than clicking the > arrow button.
The code field is the relevant one, it determines the file name of the individual blanking files. The name field is only used to show the name of individually polygons.
After these two fields have been determined, the user presses Ok and continues to select polygons for output as blanking files.