Numbering a sequence

Hi I hope you can help!!

I have a list in a table that looks a bit like this.

Week 20WednesdayMoseley ParkBar
Week 20WednesdayMoseley ParkBar
Week 20WednesdayMoseley ParkBar
Week 20WednesdayMoseley ParkKitchen
Week 20WednesdayMoseley ParkKitchen
Week 20WednesdayMoseley ParkKitchen
Week 20TuesdayMoseley ParkKitchen
Week 20TuesdayMoseley ParkKitchen
Week 20TuesdayMoseley ParkKitchen
Week 20TuesdayMoseley ParkKitchen

And what I need to do is add a secuence in the adajacent column so that the list will be numbered like this:

Week 20WednesdayMoseley ParkBar 1
Week 20WednesdayMoseley ParkBar 2
Week 20WednesdayMoseley ParkBar 3
Week 20WednesdayMoseley ParkKitchen 1
Week 20WednesdayMoseley ParkKitchen 2
Week 20WednesdayMoseley ParkKitchen 3
Week 20TuesdayMoseley ParkKitchen 1
Week 20TuesdayMoseley ParkKitchen 2
Week 20TuesdayMoseley ParkKitchen 3
Week 20TuesdayMoseley ParkKitchen 4

Does anyone know of a formula I can use to acheive this?

Many thanks

Nods