My final solution, after many tries, is this - tho the boolean to function + hyperlink works fine - the attachment list works much better & cleaner.
http://www.mibuso.com/forum/viewtopic.php?t=23298
but to connect a native database with crystal you need to install n/odbc or c/odbc depending on your version.
IN control panel->administrative tools->Data sources you setup your connection.
I never created a report in nav that calls a crystal report because it never made sence to me.
you can create unlimited reports in crystal and create a link to them in nav.
but (on average) most probably only have 100 custom nav reports, tho you can BUY more, report range 50000…50099. and I didn’t want to waste those 100 on crystal reports, it was better to save them for something else.