Please tell that I am overlooking something and that the functionality is there.

I have 2 lookups on for instance a case form; 
- 1 for the assignment group table
- 1 for the user table

I have a junction table which hold the the groups withs its members.

In the form I want to define a filter on the user lookup to limited the users selectable based on the field assignment group selected earlier on the case record.

Please tell me Salesforce supports these basic actions and that I simply overlooked it.
PS. I am interested in achieving this using VF but this is so basic that I still expect this to work on standard pages.
Really dont understand how this can otherwise be the platform to build custom apps on. I really dont.

Hi,

Since a developer is not allowed to create cases with Salesforce directly I was wondering how one can request a pilot to be activated on his development org.
It concerns the pilot "Managing Flow Triggers for Workflow (Pilot)" 

https://help.salesforce.com/HTViewHelpDoc?id=customize_wf_flow_actions.htm&language=en_US

Flow trigger workflow actions are currently available through a pilot program. Available in: Enterprise, Performance, Unlimited, and Developer Editions
For information on enabling this feature in your organization, contact salesforce.com.

Any ideas!? 

Please tell that I am overlooking something and that the functionality is there.

I have 2 lookups on for instance a case form; 
- 1 for the assignment group table
- 1 for the user table

I have a junction table which hold the the groups withs its members.

In the form I want to define a filter on the user lookup to limited the users selectable based on the field assignment group selected earlier on the case record.

Please tell me Salesforce supports these basic actions and that I simply overlooked it.
PS. I am interested in achieving this using VF but this is so basic that I still expect this to work on standard pages.
Really dont understand how this can otherwise be the platform to build custom apps on. I really dont.