RE: How stop the user from selecting prior date using workflow
Hi
If you use a Calculated field to get Today's date and tomorrow's date, it will include the time but for your requirement, it should just only consider date, not time. The same issue you will have if you use the workflow process execution time as it will include the current time.
You could try the following, assuming you have the latest version of Dynamics CRM, you can achieve what you want using the following workflow

The Cancelled step should have the message to be displayed as shown below

Once the workflow is activated, if the user tries to set any date other than today or yesterday, it will display the following and will not allow the user to save the record
