I have created a formula to prevent user to edit record after fulfiling some creterias. My formula is :
AND( RealSteer__Offer__r.Agreement_Closed__c =True,
      ISPICKVAL(RealSteer__Status__c, 'Mounted'),( RealSteer__Offer__r.RealSteer__Close_Date__c >  RealSteer__Offer__r.RealSteer__Property__r.Revenue_Close_Date__c ),

OR(ISCHANGED( RealSteer__Offer__r.RealSteer__Account__r.Name),
     ISCHANGED( RealSteer__Offer__r.Name),
     ISCHANGED( RealSteer__Blocking_Start_date__c ),
     ISCHANGED( RealSteer__Blocking_End_date__c ),
ISCHANGED(  RealSteer__Offer__r.Category__c  ),
ISCHANGED( RealSteer__Offer__r.RealSteer__Property__r.Name  ),
ISCHANGED(  RealSteer__Offer__r.RealSteer__Status__c ),
ISCHANGED(  RealSteer__Offer__r.Owner_Name__c   ),
ISCHANGED( RealSteer__Offer__r.Payment_Terms__c ),
ISCHANGED(  RealSteer__Offer__r.Blanket_Approval__c ),
ISCHANGED(  RealSteer__Offer__r.Printing_Charges__c  ),
ISCHANGED(  RealSteer__Offer__r.Mounting_Charges__c  ),
ISCHANGED(  RealSteer__Offer__r.Other_Charges__c ),
ISCHANGED( RealSteer__Offer__r.RealSteer__Approval_Status__c),
ISCHANGED(  RealSteer__Offer__r.Approved_By_Accounts__c ),
ISCHANGED(  RealSteer__Offer__r.Approved_By_Sales_Co_ordinatior__c )
))

Can anyone help me out to solve this issue?