I need to edit my formula so it displays every second true result

[PatAlex]

I am working on a cash projection spreadsheet that has the columns in a daily format. In some instances I need the expenses to repeat daily, or weekly or monthly - and I have managed to work formulas based off the days of the week or the dates that I have across rows 1, 2 & 3.

However I am stuck on the last one - getting the results to show fortnightly.

I am currently using an IF formula as follows
=IF($E$2:$CTV$2=$C21,$D21,"")
E2:CTV2 is the "days of the week" repeated over and over again
C21 is the day of the week I need the $$ to appear ie Mon or Tue or Wed
D21 is the $$ figure I need it to show repeatedly across the spreadsheet

But how on earth do I get it to show every SECOND true result so that it shows an expense every fortnight (every second Thur) rather than weekly?

Thanks in advance for any help you can provide!

[PatAlex]

I have update the title.