The only way I know to do this is to have them click on the 'Pause' button on Server or 'Pause Auto Updates' in the workbook.
This will stop the data from updating until they press the button again to play.
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While I cringe whenever I hear of Dashboards like what you described, the following helped to create a better experience (but still not ideal).
Have two dashboards in the workbook the first dashboard has all the parameters / filters on it and no visualisations, the second dashboard has the visualisations / data.
So the user will open the workbook, on the first dashboard, make their selections, and then navigate to the second dashboard to see the results.
You no longer get the real interactivity that Tableau can provide, but it sounds like this might be preferable to what you currently have.