HI Urmila,
Have you tried self registration?
Best way to register a dll which is part of the package is ,
Go to Files section in Wise Package Studio
Select the dll -> Double click the dll - > go to self registration ->
Select the Registration method -> Use order specified below...
These steps will result in auotomatic self registration in the package using
Msiexec.exe /y & /z for registeration \ unregister the dll.
Thanks,
Mani