ChaRM Automatically Insert & Populate Document Type in Scope Assignment Block

Hi All,

How can we automatically add a document type of specific type when creating or saving request for change. Currently user have to click on Insert button  under scope assignment block and chose the document type from drop down. We want this entry automatically added, for example YMHF added and populated automatically when creating YMCR, and ZMHF added and populated automatically when creating ZMCR, when we first save the request for change. We have only one document type for each request for change type and everything is working as expected but we want to automate this, it doesn't make any sense to add it manually every time.

I can't find anything in customizing and think this is possible through ABAP but don't know how. Can someone give me detailed steps??? Can it be grayed out so user don't mess with fields in this block ???

Thanks

Sajid