Change history tale for CRM BP Role

Hi Experts,

I am trying to capture the role changed date for a particuler Business Partner(BP).

Eg:

30.11.2011 09:23:12 0001000237 XXXXXXXXX BP Role BUT100 *** Created *** Sold-To Party

24.11.2011 16:03:44 0001000237 xxxxxxxx BP Role BUT100 *** Created *** Cash

We can see the role has been changed from cash to Sold-To Party . I have seen this only in change history of the BP in BP(tcode) -> Extras -> Change history -> his partner , but where exactly where it is exactly stored.

Could any one help in capturing only the Role change date (and not the record changed date) of BP. Thanks.

Regards,

Janardhan