the formula you gave is only evaluating for one row. In order to make it summarized for your data set you would need to apply a summary to to it.
I don't know your data set so I am not sure of your process here but usually there is a sum of the result which is then / by a number.
Place your MTD 2010 Tons formual on the detail section and see if you get the value you expectr for each row.
are you getting the right value?
If not, this is all a guess but maybe change your 2010 formula to
If {vw_Scale_Tickets_Material_Detail.TicketDate} in date(year(currentdate)-2,month(currentdate),1) to dateadd("yyyy",-2,currentdate)-1 then {vw_Scale_Tickets_Material_Detail.MatUnits}
then sum that and divide by 2000.
sum(
{@MTD 2010 Tons}) / 2000