Can I do that using the WF Rule.?
How should I set the criteria on the Activity Date field?
please advice.
5 answers
There are no doubt more elegant ways, but this will work.
Create a formula number field. Call it "New Field", 0 decimal places.
Activity_Date__c - TODAY()
When this evaluates to "30", trigger the rule. So your workflow rule says "when New Field = 30", fire away.