Creating a child record from a button on the parent form and automatically return back to the parent form after the child has been saved.

Kelly, 
it would be something like this

var text URLONE = URLRoot() & "db/" & [_DBID_ROOT_CAUSE] & "?a=API_GenAddRecordForm&_fid_17=" & URLEncode ([Record ID#]); 

var text URLTWO = URLRoot() & "db/"  & dbid() & "?a=dr&dfid=10&rid=" & [Record ID#];

 

$URLONE

& "&NextURL=" & URLEncode($URLTWO);