The keyword PARAMETERS

Resetting the parameters field of an existing WPProgram object to a null 
string is only possible if the last parameter for <SysCreateObject is R 
(i.e., replace). But this use of the function <SysCreateObject deletes and 
recreates the existing object. This means that all references to the 
object are deleted but not recreated. 

A workaround for this feature: Use PARAMETERS=% (or PARAMETERS=%* if the 
object should support drag & drop) in the setup string to change the 
object. This method is also necessary if you're going to change the object 
settings with <SysSetObjectData.