This can be done in a table format in your Excel workbook of audit papers. Include the account or process (i.e. Accounts Receivable or Cash Handling), objective, method, exception criteria, population, sampling unit and tolerable exception rate. For Sampling units, where exact numbers are not known (such as total number of customer accounts within Accounts Receivable), use an appropriate portion such as 1 out of 1,000.
In your spreadsheet, be sure to include your reasons for the criteria. The Sampling and Testing Plan of Controls should be part of your Excel working papers so you can turn in the entire workbook. Please be sure the tabs in the workbook are labeled appropriately.