If you make a calculation and move the record pointer, then the grid scrolls, the try this in your Calculation code

Local nRec
nRec = Recno("GRIDALIAS")
* Your calculation code here
Go nRec In GRIDALIAS


Other thing than can be is than your grid is very short and this make the scrolling automatic, try to make your grid taller, and make shure than leaves a small part of a row at the bottom
Imagine than this is a grid
+--------------------------------------------------+
| | | |
+--------------------------------------------------+
| | | |
+--------------------------------------------------+
| | | |
+--------------------------------------------------+
| | | |
+--------------------------------------------------+
+--------------------------------------------------+ && the small part of row

Hope this help

Mauricio