Updating one form with data from another form instead of copy and paste

Updating one form with data from another form instead of copy and paste

Hi
 
I have form called Study Details (parent/master) and another form called Risk Log.  There is a one-to-one relationship between the two via a field called WY_ID.
 
I have updated the Study Details form with fields from the Risk Log form, as the current arrangement is causing problems (i.e. disappearing fields due to one-to-one relationship).  For example, there is a field called Risk Type on form Risk Log, and I have added the field Risk Log to Study Details.  So basically transferred all the fields on Risk Log to Study Details.
 
I would like to migrate the information held in Risk Log for each entry in Study Details, so that I can get rid of the form Risk Log. 
 
The long way is to copy and paste across the two forms, but I have 200 records where this would apply. 
 
I have also thought about using Fetch and Update Records, however I cannot figure out how to use it for my particular circumstance. 
 
I do not want an On Add or On Submit, etc and I was wondering whether there was a way of doing some script that would update my Study Details form just this once....
 
I have explored the schedules, but got a bit lost as I am not too good with script......