ANOVA - Post Hoc Testing Problem.. Help!!

Good Morning all,

This is my first post.. I am so excited that this forum exists..
I am running an ANOVA at the moment, with a DV, and 3 IV's. Each IV has two levels (high and low). I have found significant results. My problem is that as I only have 2 levels of each IV, SPSS will not run the post-hoc tests through the Analyse ->General Linear model-> Univariate etc..
Any ideas on how I can get around this?