Print Preview of ZPL Stored format files

How do I do a print preview of a ZPL stored format file? I.e. a file with a number of fields in it. We mainly only use the PrintStoredFormat(fileName, values); function in PrinterUtil to print the label with the values filled in.

But how can I make a print preview? I know there is a built-in printer server accessible with a special URL for previewing a static zpl file. Is it possible to change this and send the field values and ZPL template filename instead?