Copying records within a file

I'm working on a program that has to copy a block of records within a file. That is to say, given a block of records, in the file FROBOZZ, with keys:

foobar 15 1
foobar 15 2
foobar 15 3
foobar 15 4
foobar 15 5

I want to duplicate the records, still in FROBOZZ, keyed as:

bozbar 7 1
bozbar 7 2
bozbar 7 3
bozbar 7 4
bozbar 7 5

or, conceivably, if there's already a "bozbar 7 1," the copies might be keyed as "bozbar 7 2" through "bozbar 7 6."

I don't relish the thought of having to keep track of the position from which I'm reading records. Can I have the FROBOZZ physical file open twice within an RPG program? Or is there an easier way to do this?