VCL component : don't paint

Hi all,
  I'm writing a component heriting from TStringGrid1.
This component have (with others things) a method that try to detect "bad" records, and select them. The problem is that when I set the Row Property (i.e. Self.Row=X), the TStringGrid allways set itself the Leftcol valut to the first non-fixed col. So I'm doing something like this :

...
I:=Self.LeftCol;
Self.Row:=X;
Self.LeftCol:=I
...

It works but if the user scoll down continuously, the component blinks because it have to paint with after row has changed, ang again once after leftcol is sets to I;

Question is : Just before the instruction "Self.Row:=X" how can I disable the drawing, and enable it juste after Self.leftcol:=I ?

regards

(hope it's clear... :-)  )

Mike