It depends on what you are trying to prompt the user to do.
However, the simplist way is to use the the "Message Popup" Step type. It pops up a dialog box, which can be customised, (eg multiple buttons, text box....)
Example
If thats not what your trying to achieve then how about using a section of code to in TestStand which loops say once a second and sends a UI_Msg (say 10000), from a loop. This UI message sends the sequence context its in (which includes a true/false flag "Locals.FinishedLooping").
You handle this UI_Msg like any other UI message. Whenever a your button is pressed on the UI it feeds its value into the "Locals.FinishedLooping" Variable in TS. When true it finishes the loop in TS and contines on..... and effectively the loop checks the UI every 1second to see if if it should end or continue.
This is only one way of doing it..... And it may not be the best way..
