Pass Total Value From Main To Sub Crystal Reports

Question

The Crystal Reports Design by DataSet(ADO.NET)
There is no Datatype on Datatable of Dataset(UI) hence I think The Crystal Reports Should
consider the all Columns DataType as a string/Text. If So than what is the actual
solution?. Is it true?.
I am facing strange problem:
MyTable scenario is :
Table Name: ProfitLoss
 Field           Datatype

 Openstock       decimal
I am trying to pass Formula Field From main to Sub reports and typed the following code at editor pane of reports:
Main Reports
Formula Fields Working is AS Below:
The Following code is in Formula Field Name is op
 ToNumber({ProfitLoss.openstock})
The Following code is in Formula Field Name is op1
 sum({@op})
The Following code is in Formula Field Name is op2
 WhilePrintingRecords;
 Shared NumberVar mytotal:= {@op1}
Sub Reports:
Formula Fields Working is AS Below:
The Following code is in Formula Field Name is mm1
 ToNumber({ProfitLoss.puramt})
The Following code is in Formula Field Name is mm2
 sum({@mm1})
The Following code is in Formula Field Name is mm
 WhileprintingRecords;
 Shared NumberVar mytotal;
 mytotal;
The Following code is in Formula Field Name is TT
 {@mm2}+{@mm}
It's shows SUB-Reports's Total Only. It's not calculating main form total…..
In Short Main Report's Total not returning or consider. In this case what is the solution?.