# Workflow

## How to Execute Userexits Automatically at Process Start or Finish

| ### What to do:
| As a prerequisite for this example you must have completed the examples Create an Ad-hoc Process or Create a Process from a Process Template.
| Select Start > Workflow > Processes in Definition. The Process Definition mask is displayed.
| Click to update the mask or search the process Purchase Requisition.
| To change to Edit mode click .
| Go to the Triggering of userexit section.
| Click the At Process Start field and enter the userexit to be executed upon initialization of the workflow process.
| To save the entry click .
| In order to start a userexit after the process completion, enter a corresponding userexit to the At Process Finish field.
| The pre-action userexit of a main process is executed synchronously with the plm server. Thus, a possible output message will be visible in the message window of the client. The post-action userexit of a main process, as well as the pre- and post-action userexit of a sub process, are always executed asynchronously like a batch operation in a separate started server without UI.
| Be aware that the pre-action userexit of an accidentally started sub process is already executed synchronously with plm server before the error message appears, thus a sub process cannot be started from application server.