Interpreting time invariant covariate - repeated measures

I conducted a 3 x 2 x 2 x 2 repeated measures ANOVA with 2 time invariant / between subjects covariates. While covariates did not have significant result on their own or on parameter estimates, they did interact significantly with the IVs, which is what I'm interested in.

I have not been able to find anything to help me interpret what is happening in these interactions (for my level of understanding, or that's suitable for SPSS). I came up with calculating the change score between the interacting variables (determined by contrasts within subjects), and correlating this change score with the covariates (partial correlations controlling for the other covariate as they are related to each other). This seems to be giving me relevant information, but I can't find literature to suggest this is a valid way of interpreting this kind of interaction. Any thoughts?