IS Tech Support has a $49.95 utility that can Find and Replace, Adjust or Delete based on up to 6 different filters that could be used to clean up the file. There is no import/export capability for the PO Receipt file although you could hook to it using Access if you know how to use ODBC to connect to the file.
See
http://www.istechsupport.com/addonut.asp if you are interested in the utility program. Works on any version of DBA.