Formula to Insert Fortnightly Bills in Table

Hello,

This is my first post and I'm hoping to get a bit of help with creating a formula that I can use on a finance table that I've created.

I am attempting to forecast my personal finances and want to insert fortnightly payments into a column automatically.

I've managed to do this for my monthly payments through using the following formula:=IF($J21=BJ$14,BJ$17,""). For context, $J21 is the first cell of the column that captures the day value of the date which is in $I21, BJ$14 is the day of the month that the particular payment comes out (in this case the 4th) and BJ$17 is the value of the payment ($100). After entering this formula and dragging it down the entire column, $100 appears whenever the date is the 4th of the month.

Does anyone know of a way that I could obtain the same result with fortnightly payments? Also, if you're feeling especially generous feel free to come up with a formula for quarterly payments too.

My apologies if this is a silly question, I learn Excel by reverse engineering a lot of formulas that I come across in random spreadsheets (hence my display name). My knowledge definitely isn't up there at the moment and I might be missing something obvious.

Thanks in advance,

Mr XL. R Engineering

Thank you,

Example spreadsheet attached. Red columns are for monthly payments, yellow are for quarterly.