Automatic panning

hi everyone,
I am working on a mdl application to dynamically pan the view.
this shud trigger only when the cursor reaches the corners of the view.

this app shud recenter the screen around the last point clicked by user.

i have gone thru the earlier discussions and found out this code

viewRange[0].z = viewRange[1].z = 0,

mdlCnv_IPointToDPoint (&cursorPosition, &statedata.current.uors);

viewRange[0].x = cursorPosition.x - 100*tcb->subpermast*tcb->uorpersub;
viewRange[0].y = cursorPosition.y - 100*tcb->subpermast*tcb->uorpersub;
viewRange[1].x = cursorPosition.x + 100*tcb->subpermast*tcb->uorpersub;
viewRange[1].y = cursorPosition.y + 100*tcb->subpermast*tcb->uorpersub;

mdlView_setArea (1, viewRange, NULL, 10.0, 1.0, NULL);
mdlView_updateSingle (1);

but when i run the command,
screen runs away.
also when i look the cursor position it seems to change too much
from +ve to - ve values with the slightest change in the mouse position

any help is appreciated..
TIA

Suneel.