Adding Subreport Total To Main Report Total

Hi, can anyone help?

I have created a Report using Visual studio-the report displays a subreport within it.

On the Subjective Report I have 12 values for each month of the year.

For the first month the value is =sum(Fields! Month_1.Value), and I
have named this text box €™SubRepM1€™
The name of the subreport is €˜subreport1'.

On my Main Report, again I have 12 values for each month of the year.
For the first month the value is =sum(Fields! Month_1.Value)*-1, and I
have named this text box 'MainRepM1'
The name of the main report is 'GMSHA Budget Adjustment Differentials'

The report displays both of the subreport and main report values
but I now need to total these values together for each month in order to
produce a grand total.

I have tried using the following to add the totals for Month 1 together,
=subreport1.Report.SubRepM1 + MainRepM1
but this does not work and I get the following error message €˜The value expression for the text box 'textbox18'contains an error [BC30451] Name subreport1 is not declared'.

I feel that it should be a simple matter of adding the two sets of values together but I€™m having major problems trying to get these totals to work.

Can anyone help, thanks