Access autonumbers

[eastman.uk]

Hi, is there any way I can use autonumbers in MS Access 2003 with a compound key, so that the number begins at 1 for each instance of the other part of the key? Heh, that doesn't make much sense, here's an example of what I want:

SmithJ - 1

SmithJ - 2

SmithJ - 3

JonesR - 1

JonesR - 2

BrownP - 1

BrownP - 2

BrownP - 3

BrownP - 4

and so on... Any simple way of doing this? I'm quite a n00b to Access, so any help greatly appreciated! Thanks!