I have a many to many relationship between two main files (volunteers and clients) and in both of these files I use a portal containing data from a join file to move between the related records in the two main files.

Because the links need to be created using drop down lists of the names of the people in the other file, I am using the volunteer name and Client name as the match fields.

Naturally, when either of the names change (say I add a middle name at some later point, or someone gets married and changes their name) the link is immediately lost with the person/people in the other file.

Is their any way that I can use recognisable data when choosing someone from the opposite file, and yet relate the files using an unchangeable bit of data such as a unique record number?

I have tried all sorts of things but without success so far.

I suggest using auto entered serial numbers as your keys. Make your value list show the name as the second field.