How to measure a moderator: 2 independent variables and one moderator (median split)

Hello to everyone,

I have some problems with my diploma work and I really need your help.

I am trying to measure a moderating effect on my sample. I looked into the literature and I am still unable to find the answer. What ever I came onto is regarding one IV and one moderator.

My IVs are nominals (1 and 2 values). I am asked to perform a median split on the moderator. So, what I know is that I have to multiply the moderator by the IV. How is this done with two IVs? Do I have to multiply every IV separately, or I just multipy all three of them?

Can you please give me some insights? Literature is also fine as long as it is also SPSS related. I came across so many formulas... that I can hardly go throught them.

Thank you!