Hi Dough,
Creating a new entity and linking it might be a long winded solution.
I had a client who wanted their users to select a Picklist Value which would
automatically populate the Subject Text box. The Subject Text box can either
be disabled or enabled on the form
Steps
Create a Picklist Attibute call it Subject List with a list of Subjects and
put the jscript below into its onChange event.

//This script will populate the Subject field on the Activity type with a
Subject Value from the list

var oCallResult = event.srcElement;
var oSubject =document.crmForm.all.subject;
oSubject.DataValue = oCallResult.SelectedText;




Cheers
Nash





"DoughnutLover" wrote: