What information do you need in your grid? If it’s just one column then this technique works very well.
The other thing that you can do is run a Max() function on your DMR table with your applicable field (that’s a calculated field), then group by everything else on the grid, (That’s assuming that the data in the rows is duplicated only because of the multiple rows in the DMRAction table.)
Let me know if that’s enough help or you need more details. You didn’t give a whole lot of information about the structure of the rest of your BAQ, so I’m not 100% sure what the right answer is.