Doing a SUMIF of durations in Numbers

I am a musician with a very long list of quintet music, listed by composer, title, etc. and including song duration in MM:SS format. When creating a set list, I would like to put a checkmark into a column in the song's row to include the song in the list, which would then automatically add the duration to the total set time. I have tried the SUMIF function, but it does not work (sum Duration if Set value is 1 (true)). I have tried to debug by simply summing the Duration column, but that yields bizarre date results. What am I doing wrong? How can I fix it?