MODPHOT allows you to change records in a photometry file. The program asks for the number of the record being changed. You can enter or change coordinates or identifying labels. You can also delete records. You should use the command 'PRINT PHOT' (which can be redirected) to get a list of the record numbers before you call MODPHOT.
A word of warning: The program renumbers the photometry records if any are deleted. So if you, for example, delete record 17, number 18 becomes 17, 19 becomes 18, etc.
If you want to save changes made by the MODPHOT command, you must use the 'SAVE PHOT=filename' command.