It looks like some arbitrary function of your own or what someone gave you. All we can tell you is what you seem to already know. You need to pass in arguments for old and handles. If there is no indication in the function as to what those should be then unfortunately you have bad code to work with and will have to try to work it out or abandon the code.
Judging by the error message, old is expected to be a struct so goodness knows what fields it is expected to have, it could be anything. The fact it has a field called 'allVarNames' is in itself not an encouraging thought as to what it should hold. handles sounds like it would come from a GUI, but again, who knows?
