SSRS - Print subtotals in footer

Hi.

I have a question about AX 2012 and SSRS. I would like to print in the footer of each page sub totals but I have no idea.

For example:

Site 1:

Value A   Value B    100
Value C   Value D    110

Subtotal: 210   {Footer of the Page}

Site 2:

Value E   Value F     300
Value G   Value H    410

Subtotal: 920   {Footer of the Page}

Etc.

I hope somebody can give me a tip.