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EquationTrekker for system of two 1st order ODEs

Is it possible to use the EquationTrekker package to plot solutions of a 
system of two first-order ODEs?

With Mathematica 7.0.1, I try:

       {x'[t] == 2 x[t] + 3 y[t], y'[t] == x[t] - y[t]},
       {x, y}, {t, 0, 20},
       PlotRange -> {{-5, 5}, {-5, 5}}]

Up pops the expected EquationTrekker graphics window. And if I then 
right-click somewhere in the xy-plane there, sometimes nothing happens 
and sometimes I get a point.  (Except for the origin, which is an 
equilibrium point, all other trajectories for that system are either 
half-lines or hyperbolic arcs.)

Note that the output from evaluating "?EquationTrekker" includes the 

   "EquationTrekker[eqns,{x,y},{t,Subscript[t, min],Subscript[t, max]}] 
opens a graphical interface for specifying initial conditions and 
plotting the resulting numerical solution to the system of two first 
order ordinary differential equations eqns for the functions x and y"

Murray Eisenberg                     murray at
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

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