Hi Stephen;
Check in LabVIEW's help for the following examples:
Zoom Graph - Under "Fundamentals -> Graph and Chart Examples"
Smith Plot with Zooming - Under "Advanced -> Picture Control Examples"
"Zoom Graph" is also available at NI at:
http://zone.ni.com/devzone/explprog.nsf/6c163603265406328625682a006ed37d/22fd93d924d7f5d08625685400697ce5?OpenDocument
Regards;
Enrique
www.vartortech.com