What you are asking is an easy in LabVIEW 6.x because there are built VIs for this sort of thing. In LabVIEW 4.x, it is another story. Upgrading to LabVIEW 6 would be the easiest and fastest way to get to a solution. If you want to use LabVIEW 4.x, you will have to do some coding. I suggest the following algorithm. Take the difference of the functions. Notice that when the difference function crosses the x axis, the functions have the same value. You will now need to look for sign changes in the difference function to isolate where the function equals zero. This is commonly called the sign test, and in a nutshell, it means that changing from positive to negative implies that the function crossed the X axis.
Jeremy Braden
National Instruments