PLEASE HELP -Syntax for GLM simple effects and comparisons

My design for my experiment is a mixed model-
Within subject factor= exposure (Diff_I, Diff_S, Diff_V) and the between subject factor is VIS (High, Low)

Would someone please be able to give me the syntax for working out the simple effects of exposure at each level of VIS, and the simple comparisons for the effect of each exposure on VIS.

Also.... i need the syntax for VIS and each level of exposure.

Does this make sense?

Would the syntax also provide me with the correct 'dfs' and MSE for each test, that I will be able to report in the write up?

I will be very grateful for any help! :)