interaction help...

#1
i have an nominal IV with four levels, an ordinal IV and ordinal DVs. I want to test for an interaction effect in which high levels of the ordinal IV produce high levels of the DV in just one of the nominal IV levels. I have only learnt how to create an interaction term for SPSS GLM for ordinal variables. Can anyone help me with how to carry out an interaction analysis for a nominal variable with 4 levels? Thanks in advance :)