Currently, this is possible with the built in function. Might make a good one for the Ideas section. There are some possible workarounds, such as finding the desired column total on only one sheet and the rest of the worksheet on a separate sheet. Then, place the two worksheets on a dashboard together.
Hope this helps!
I don't know of a way to do this using the two-pass totals, however it is possible using a custom calculation and a duplicated dimension pill. In the attached, I used the techniques from these two posts:
The calculation is a WINDOW_MAX(SUM([Sales])), with a Compute Using on the Market Size (copy) dimension. In the row grand total on the right, this takes the max of sum(Sales) for each Market Size within each Market. In the Column grand total on the bottom, the sales are summed up across all Markets, so the WINDOW_MAX does nothing.
The one extra bit to turn off mark stacking is to use Analysis->Stack Marks->Off.
Thanks much Tracy and Jonathan.
I will try these out and reply back.