User Perform Script on Server script and create a script that runs with a Script Parameter for each record on that list.
Go to first record
Perform Script on Server [SerialNo for that record as a ScriptParameter]
Go to next record finish after last
The Script that runs Perform script on Server
Go to layout (the right one for your)
Set field X to Script paramter
Do the action
Johan's basic advice is sound. Another option to look at is Replace Field Contents. It processes considerably faster than Set Field in a loop, but is less error-tolerant.