How to attach line item which is not part of sub report

We are builing a grid with transactions, but would like to put a "total" at the end of the grid, even if contents spils to another page. We are using sub report though and could not attach another line items which is the total, because it's not part of the the transaction list.

We tried to put the item in the footer, but it doesn't snap to the sub report/grid.

Thanks