I recently created a validation rule preventing all users not designated as "System Admin" from changing the stage of an opportunity to closed won or closed lost.  However, I see that the opportunity owner can still make changed regardless of this VR.  Is there anyway I can restric the record owner from making these changes so that the System Admins have exclusive access.  I have professional edition by the way.

And here is my VR 

AND( 
$UserRole.Name <> "System Admin", 
ISCHANGED(StageName), 
ISPICKVAL(StageName,"1 - Closed Won"), 
ISPICKVAL(StageName,"0 - Closed Lost"))

I recently created a validation rule preventing all users not designated as "System Admin" from changing the stage of an opportunity to closed won or closed lost.  However, I see that the opportunity owner can still make changed regardless of this VR.  Is there anyway I can restric the record owner from making these changes so that the System Admins have exclusive access.  I have professional edition by the way.

And here is my VR 

AND( 
$UserRole.Name <> "System Admin", 
ISCHANGED(StageName), 
ISPICKVAL(StageName,"1 - Closed Won"), 
ISPICKVAL(StageName,"0 - Closed Lost"))