How to add Relative Time entries for FilterBuilder Dates

I use FilterBuilder to allow users to search a list of entries. One of the cells contains a date and I need users to be able to filter based on the weeks of the day. Basically, I want to be able to construct a filters like:
Date events on the filter builder can be filtered as: 'Today', 'Yesterday', 'N days ago', etc. However, I would like to add a couple of entries into this combo box of the form: 'Monday current week', 'Sunday current week'. What is the best approach to do this?

Thanks in advance,

SmartClient Version: v9.0p_2013-11-09