Ah, interesting. Yes this sounds like it could be the solution I require. It sounds like this is what macropod alluded to in his response. Of course, if the user has macros disabled due to security settings this wouldn't work, but that's the same problem as with any macro enabled document anyway.

Thanks very much I'll give that a try.

Thanks also to Charles Kenyon for his response - you mention some concerns that I share (user will overwrite the .docm).