Day/TimeStamp within Formula

I have several fields that need to be calculated. One is simple enough "Current Count" - "Old Count" gives me the "Difference". Which in my field this is the formula for "Difference" = subtract($new_bag_count_c,$old_bag_count_c). 

But I need a value to "freeze" every Wednesday at 2 pm EST. So I made a field called "Bag Count Weekly". 

Here is the formula: ifElse(equal(dayofweek(today()),4),$new_bag_count_c,$old_bag_count_c) 

I can't figure out how to add the TimeStamp into the formula, not even sure if I have the rest of it correct or not either. Appreciate the assistance.