Lock/Unlock Stored Procedure during execution time.

CREATE PROCEDURE [dbo].[Your_SP_Name]
(
  // Declare Your Parameters.
)  
AS
BEGIN	
      SET NOCOUNT OFF;  
		
      SET TRANSACTION ISOLATION LEVEL REPEATABLE READ
      BEGIN TRANSACTION
      
        DECLARE @LockResult int;
         EXECUTE @LockResult = sp_getapplock 
         @Resource    = 'RepeatableRead_TRANSACTION', 
         @LockMode    = 'Exclusive',
         @LockTimeout = 0
            
      // Write Your QUERY  Here.
	
	EXECUTE sp_releaseapplock 
            @Resource = 'RepeatableRead_TRANSACTION'
	COMMIT TRANSACTION
END