orgmodel determination

Hi,

Iam creating the activity.

Iam entering the activity partner(customer).

I need to determine the org unit of bussiness partner using his partner number.

what i did i created one determination rule and assign it to org profile ,and org profile is assigned to tranaction type.In determination rule i used is sap given rule

10000148(Org unit by means of partner number).

In org model attribute (partner number) i assign the

bussiness partner number.

when i create the activity i enter the partner.

but htere is no value in or unit in activity.

why it happens.

please tell me how should i proceed.

thanks

swathi