Update database record with Function in SQL Server

Please help i would like to return the division as the returned values

ALTER PROCEDURE [dbo].[DIVISONUPDATE] AS 
BEGIN
    DECLARE @admno nvarchar(50)
    DECLARE @engrade INT
    DECLARE @engscore INT
    DECLARE @sstscore INT
    DECLARE @sstgrade INT
    DECLARE @sciencegrade INT
    DECLARE @sciencescore INT
    DECLARE @mathscore INT
    DECLARE @mathsgrade INT
    DECLARE @Totalgrades INT
  
    DECLARE @Sum INT = 0
    DECLARE @Counter INT, @TotalCount INT
   
    SET @Counter = 1  
    SET @TotalCount = (SELECT COUNT(*) FROM temp)   
    WHILE (@Counter <= @TotalCount)
    BEGIN
        SET @admno = (SELECT admno FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
        SET @engrade = (SELECT engrade FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
        SET @sstgrade = (SELECT sstgrade FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
        SET @sciencegrade = (SELECT sciencegrade FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
        SET @mathsgrade = (SELECT mathsgrade FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
        SET @Totalgrades = (SELECT Totalgrades FROM (SELECT ROW_NUMBER() OVER( ORDER BY (SELECT 0)) RowId,* FROM temp) t WHERE t.RowId = @Counter)
     
        IF @Totalgrades >=4 and @Totalgrades<=12
        BEGIN
            IF @engrade='9' Or @sstgrade='9' Or @sciencegrade='9' Or @mathsgrade='9'
                UPDATE temp SET Division = '2' WHERE admno = @admno
            ELSE
                UPDATE temp SET Division = '1' WHERE admno = @admno
        END
        ELSE IF @Totalgrades >=13 and @Totalgrades<=23
        BEGIN
            IF @engrade='9' Or @sstgrade='9' Or @sciencegrade='9' Or @mathsgrade='9'
                UPDATE temp SET Division = '3' WHERE admno = @admno
            ELSE
                UPDATE temp SET Division = '2' WHERE admno = @admno
        END
        ELSE IF @Totalgrades >=24 and @Totalgrades<=29
        BEGIN
            IF @engrade='9' Or @sstgrade='9' Or @sciencegrade='9' Or @mathsgrade='9'
                UPDATE temp SET Division = '3' WHERE admno = @admno
            ELSE
                UPDATE temp SET Division = '3' WHERE admno = @admno
        END
        ELSE IF @Totalgrades >=30 and @Totalgrades<=34
        BEGIN
            IF @engrade='9' Or @sstgrade='9' Or @sciencegrade='9' Or @mathsgrade='9'
                UPDATE temp SET Division = '4' WHERE admno = @admno
            ELSE
                UPDATE temp SET Division = '4' WHERE admno = @admno
            END
        ELSE IF @Totalgrades >=34 and @Totalgrades<=36
        BEGIN
            UPDATE temp SET Division = 'U' WHERE admno = @admno
        END

	
		 ELSE IF  ISNULL(@Totalgrades,'') = '' 
        BEGIN
		   UPDATE temp SET Division = 'X' WHERE admno = @admno
		   END
        SET @Counter = @Counter + 1
        CONTINUE;
    END
END