Grand total problem

i m having 2 tables in Access
T1 AND T2

T1 is having following fields
1] file1Id (Num)
2] Description (txt)
3] Amt (num)
4] typeId (txt)
5[ date (date)


T2 is having
1] file2Id (num)
2] file1Id (num)
3] description (txt)
4] amt (num)

from this 2 table im generating a cystal report
group on file1Id
and rpt format is
-------------------------------------
date | description | DAmt | CAmt |
------------------------------------

now the report should in following manner

if T1.typeId ='1' then T1.Amt in Damt column in group header and their
child record from T2 in details of rpt in Camt column

if T!.typeId='2'then T1.Amt in CAmt column in group head and their
child record from T2 in details of rpt in Camt column of

now I have taken 2 formula fields in group header
1] Damt and place it in groupheader column of rpt the
formula is ( if T1.typeId='1' then T1.Amt)
2] Camt place in group head
formula is ( if T1.typeId='2' then T1.Amt)

for details i have again taken 2 formulas
1] dtlDamt in detail column
formula is (if T1.typeId='2' then T2.Amt)
2] dtlCamt in detail column
formula is (if T1.typeId='1' then T2.amt

for subtotal i have
1] subDAmt formula is ( Damt + sum({dtlDamt},{T1.File1Id})

2] subCamt formula is ( Camt + sum({dtlCamt}, {T1.FileId})

all this is working perfectly
but can any body help me in getting grand total of this 2 columns