Since this was just resurrected again.  I have no idea what RCV is doing and maybe that's a QB Online thing, but they were referencing QB Desktop, not Online.  For the current version of QB Desktop you don't have to create a Custom Field, just go to Reports - Vendors & Payables - Vendor Contact LIst -> Customize -> in the columns box type print, then below "Print on Check as" should show up.  Check it. 

Viola there's a report of vendors with that field also.  I do not know if it's available in a similar fashion in QB Online.  Once you have this, now you can do a vlookup in excel against the Print On Check As field.  If it exists, use that, if it doesn't, use the Vendor name.  Create your Positive Pay file from that.  You can look up Adevity and we could help you one on one, but as already stated, if you don't know how to do the above you may be better off just buying the previous guys program.