Is this something particular to how Canada does mortgages? In the US, a bog standard mortgage is 12 payments a year, with all interest for the month accruing on the 1st day of each month. It's pretty trivial to put that into Excel and use the IPMT function (and related ones like PMT) to spit out the interest being paid in a given month. It's always been dead-on accurate for me.

Maybe this is just one little upside of mortgage terms in the US being dictated mostly by the gov't through fannie mae and freddie mac.