There are two ways of accomplishing this.
Create a provision which blindly refreshes any of the diagnostic nodes you use in your environment (IPPing, UDPEcho, Download, Upload). Use a preset which listens for the 8 DIAGNOSTICS COMPLETE event to kickoff the provision. This is the easiest route.
The better approach requires a lot more work. You need to create a v-param to track which diagnostic test was initiated. Then, in the provision script, use the value of your vparam to determine which parameter to refresh. This is the approach I use.