Sharepoint 2013 Workflow using SPD

Hi,

I have a Sharepoint List that contains seed calendar entries as follows:

Course Name
Date and Time
Lecturer
Room
Adult Participant Count
Child Participant Count

I was hoping the use the above seed calendar entries to populate a perpetual diary of weekly courses through an SPD Workflow, but only up to four weeks in advance.

So far, I have an SPD workflow running in a perpetual loop, and I thought I would be able to use the following approach to achieve my aims, but I cannot see a way of using the Weekday function to wrap around the [Today] value.

Pseudo-code a follows:

IF WEEKDAY(Course Date0 = WEEKDAY([Today])
 - Add 28 days to today's date and create a new list item
END
PAUSE for 1 DAY

The adding to a list bit is simple enough and so is the pause, but I cannot seem to be able to get the IF bit working. Any ideas?

Surely SPD can't be as basic as not allow simple functions to be used in loop conditions. I am new to SPD to perhaps I am missing some obvious user-interface bit.

A couple of colleagues have suggested calculated columns but they don't like the [Today] function as they need to store static as opposed to dynamic values.