New template user remove text in surname field

Hello,

I have a question related to our naming convention for our username template in ADManager Plus.
In our Active Directory we need to create all users with a maximum of 8 signs.
If a user already exists with this name, it will be creating the new user with a following number (1/2/3 etc.)
I already configured this in the template, and this is working fine.

Example:
Firstname: Ronald
Initials: RH
Surname: de Rosing

My question is, how can i accomplish it to remove a particular text in the surname field?
I want to create the user "Rosing de Rosing" with a username of "rrosing", so without the text "de"
My current configuration for the username is: %givenName%1[L]%sn%[L]

Hope someone can help me out here how to accomplish this.