Collection of participants for Assigned Activity

Hi.

I need to set collection of WTUser as Assigned Activity participants. And all of them are required for this activity.

All WTUsers are initialized dynamically by code invoked from workflow.

It works with single WTUser. But i can not find out number of users in advance.

I tried to use WTGroup but there was exception because of my temp wtGroup is not persistent.

Is there solution of my problem?

Thanks.