Hi Kousy,
Try "property node" of your graph, and see the description of these properties:
X scale > Scale fit
Y Scale > Scale fit
X Scale > Range > minimum and maximum.
Y Scale > Range > minimum and maximum
Palette > Active tool
you may want to autoscale your graphs to maintain the original view, or you may want to save the maximum and minimum values of x and y scale of your graph before zooming and then retrive those values and write them again to graph properties.
Hope this can help