  We use semiclassical methods to calculate the probability of inducing a
change of topology via a high-energy collision in the SU(2)-Higgs theory. This
probability is determined by a complex solution to a classical boundary value
problem on a contour in the complex time plane. In the case of small particle
number it is the probability of instanton-like processes in particle
collisions. We obtain numerically configurations with the correct topological
features and expected properties in the complex time plane. Our work
demonstrates the feasibility of the numerical approach to the calculation of
instanton-like processes in gauge theories. We present our preliminary results
for the suppression factor of topology changing processes, which cover a wide
range of incoming particle numbers and energies below the sphaleron energy.
