zoooooom

it depends how you are displaying your graph. Are you using a graph control, or are you drawing it in a picturebox?

hi,
sory i cant distinguish between using graph and picture box..as mentioned in ur ques.
i m drawing a line graph with several point with the command

e.graphics.drawline(p1,p2);
and  im geting this point with the function
points p1 =new point(this.clientrectangle.left,...........)

i hope i made it clear

Ok, i was trying to determine if you were drawing the graph yourself, which you are. You can use transformations on a graphics object to acheive a zoom effect.
Firstly, you need to determine the offest to centre on the area you want to zoom in on and use a TranslateTransform to move the graphics object, then use a ScaleTransform to increase/decrease teh size of the graphics object.
Theres are some great tips on GDI+ at bobpowell.net that you could scan through.