"yshridhar" wrote...
Thank you Mr. Bernie. I am sorry to say that it had some problem. I am
giving the data. I changed the formula instead of column B - column C

reformatted
Section__ID No__Marks__Rank-formula__Actual Rank
1A_______1A1____150________1____________1
1A_______1A3____150________1____________1
1A_______1A2____149________3____________2
1A_______1A24___149________3____________2
1A_______1A4____149________3____________2
1A_______1A17___148________6____________3
1A_______1A20___148________6____________3
1A_______1A5____148________6____________3
1A_______1A10___147________9____________4
1A_______1A12___147________9____________4
1A_______1A21___147________9____________4
1A_______1A16___146_______12____________5
1A_______1A22___146_______12____________5
1A_______1A6____146_______12____________5
1A_______1A11___145_______15____________6
1A_______1A23___145_______15____________6
1A_______1A19___144_______17____________7
1A_______1A25___144_______17____________7
1A_______1A13___143_______19____________8
1A_______1A18___143_______19____________8
1A_______1A8____136_______21____________9
1A_______1A14___127_______22___________10
1A_______1A26___127_______22___________10
1A_______1A9____102_______24___________11
1A_______1A15_____0_______25____________0
1A_______1A7______0_______25____________0

If this table were sorted by Section in whatever order then by Marks in
descending order, and this table spanned columns A to E with column headings
in row 1 and the first row of student records in row 2, the rank formulas
could be simplified to

D2:
=IF(C2=0,0,IF(A2<A1,1,IF(C2=C1,D1,D1+1)))

Fill down as needed. If this table would be sorted only by section but
within section student records could be in any order, you'd need to use

D2:
=IF(C2=0,0,SUMPRODUCT((INDEX(C$2:C$1001,MATCH(A2,A $2:A$1001,0))
:INDEX(C$2:C$1001,MATCH(A2,A$2:A$1001,0)+COUNTIF(A $2:A$1001,A2)-1)C2)
/(COUNTIF(INDEX(C$2:C$1001,MATCH(A2,A$2:A$1001,0)): INDEX(C$2:C$1001,
MATCH(A2,A$2:A$1001,0)+COUNTIF(A$2:A$1001,A2)-1),INDEX(C$2:C$1001,
MATCH(A2,A$2:A$1001,0)):INDEX(C$2:C$1001,MATCH(A2, A$2:A$1001,0)
+COUNTIF(A$2:A$1001,A2)-1))+(INDEX(C$2:C$1001,MATCH(A2,A$2:A$1001,0))
:INDEX(C$2:C$1001,MATCH(A2,A$2:A$1001,0)+COUNTIF(A $2:A$1001,A2)-1)<=C2)))+1)

Modify the range addresses for your actual table.

You'd be much better off sorting the table by section AND by marks and using
the simpler formula.