You'll need a script in your business rule to do this. When a request is submitted, the REQ is created first, then the RITM close behind it. SCTASK(s) are only created as your workflow dictates, or if you allow manual creation from the related list on the RITM. It sounds like it will be best to have the business rule running before insert on the sc_req_item table. The script will set the priority based on this variable, then Glide to the REQ to do the same. You can then create a second business rule before insert on sc_task to set the priority to that of its RITM.
So for the first rule on sc_req_item, the script would look something like this - depending on your variable name and the Value of the choice list item (can be different from the Text/label)
(function executeRule(current, previous /*null when async*/) {
if(current.variables.variablename == "choice list Value"){//replace variablename and choice list Value
current.priority = 2;
//now lookup the REQ attached to this RITM and set its Priority to the same
var req = new GlideRecord('sc_request');
req.addQuery('sys_id', current.request);
req.query();
if(req.next()){
req.priority = 2;
req.update();
}
}
})(current, previous);
You can specify an Item in the Filter Conditions, so that this rule only runs for this item - or it won't do anything otherwise if that variable name and value isn't found in other items.
For the business rule running before insert on sc_task, with the Filter Condition Request Item.Item is <<this catalog item>>, on the Actions tab you can Set filed values Priority Same as Request item.Priority. In case you're not familiar, these 2 references to Request Item. another field are found by showing the Related Fields at the bottom of the fields list, then selecting the field within the Request Item fields.
