I am trying to create a Validation Rule that allow users to move stages back only if certain fields values are selected. For this Opportunity validation Rule below, the stage can only move back when the picklist value is not "Medium". So I move it back with value <> "Medium", it works just fine. But if the Value is "Medium", the VR that I have now fires when I move the stage forward as well to Stage 4-6 and Closing and I cannot save anything. Is there something that I am missing?
AND( CASE( StageName , "Stage 2",2, "Stage 3",3,0) < CASE( PRIORVALUE(StageName), "Stage 2",2, "Stage 3",3,0) , !ISPICKVAL( Level_of_Confidence__c ," Medium" )))