I'm trying to compare regression models of the same form between three groups. Each model has two continuous independent variables. I need to assess the similarity or not of the two slope coefficients and intercepts.

My reading so far indicates that I should be trying to complete an appropriate ANCOVA analysis, perhaps via multiple regression with dummy variables. I have some standard texts (Kleinbaum, for example) and am working through the problem but so far I have not come across an example that involves three groups and two IVs. Does anyone have an example solution for three groups and two IVs that I can use to ensure that I am on the right track? Ideally, this would be SPSS based. Any general advice also gratefully received.