Datagrid V Scroll Position Changes on Editing

I Have a Datagrid based application, which accepts numeric fields from the user. The grid is displaying some 2000 rows, and is having the height as 300 px. The requirement is when ever a row is modified by the user , it has to be shown in red color, rest all rows remain the same. For doing this I re paint the whole grid on the CELL CHNAGE event of the editable column and the edited row comes in red. The problem is Suppose user selects 1000th Item for editing , which while editing is seen at the top of the window. When the user edits the field and does a tab out the whole grid is repainted and the edited row does not remain in its original position, but is seen a bit lower side of the grid. This behaviour of the grid is confusing the user, as the user gets lost and surprised when the changed row is misplaced after editing the field. Can someone please let me know the reason as to why this is happening and if possible suggest a suitable solution for this.