In case this helps someone else out...
I'm either doing something wrong, or the SetEntry and GetEntry don't work. To get around this, I added a reference to Microsoft Excel and used this method:
boolstatus = dt.Attach(); Worksheet ws = (Worksheet)dt.Worksheet; Range rng = (Range)ws.Cells[3, 2]; rng.Value2 = 3; dt.UpdateTable(2, true); dt.UpdateModel(); dt.Detach();
This works for updating the spreadsheet and the models