We propose a structured, training sequence based method to find the parameters of a spatio-temporal co-channel interference (CCI) rejection filter. By exploiting the inherent structure of the CCI, it is shown that the number of parameters that are to be estimated can be made independent of the spatio-temporal filter order. It is further shown that by taking advantage of the desired user's known protocol structure, the parameters can be estimated using a semi-blind technique. Simulation results indicate that by taking the structure into account, for short training sequences, considerable gains are achievable compared to an unstructured method.