Hi,
You can accomplish this via a before business rule on the catalog task table, with conditions such as "state changes to awaiting caller" AND dot-walk to the request item by scrolling to the bottom of the field options in the condition builder and selecting "show related fields":
and then choosing request item > name contains "Hardware request" or however else you want to filter for this one request item AND that the task (not request item) short description contains "Check Stock" or again, however you want to filter for the task short description/field.
Then you can select the advanced checkbox and then use script and set it as appropriate such as:
current.comments = "Hello world!";
DO NOT USE current.update() to update the record, the before business rule will do that automatically for you.
