Hi,
This can be achieved by using SelectRange method in the Selections property. The following is the code snippet, please try it and let us know if you need any further assistance.
this.gridControl1.Selections.SelectRange(GridRangeInfo.Cell(a,b), true);
Here I attached my sample,
http://www.syncfusion.com/Support/user/uploads/select_a_cell_42e564fd.zip
select_a_cell.zip Best Regards,
S.Shyam.