vista - launch process as different user with elevation from non privileged process

[starrysky]

I have a process (A) that runs at user login on many systems. The users are usually not Administrators. I want the process to be able to launch a process (B) to do Admin level tasks. I have a common Administrator account ( called sysuser) on each system. I can use this to run process B in. Users cannot know the password to this account.

I have had little success with .net process,process startinfo so far in Vista

if process B does not have a 'RequiresAdminL evel' manifest then vista runs it okay as sysuser but at least privilege level. If I put a 'RequiresAdminL evel' manifest in process B then I get an exception 'Requires Elevation' and B does not run.

The only way I can get the system Elevation prompt is if I ...
1/ set processstartinf o.verb="runas"
2/remove the Username/password of 'sysuser'

then the elevation prompt occurs but users are left being asked to enter a password to a priviliged account they are not allowed to know.

I want the user to just have to accept the elevation prompt and then B run elevated under the 'sysuser' account. Anyone any ideas?