I have a folder that contains multiple csv files, like so..

f-100713 XXX.csv
f-100713 XXX.csv
f-100713 XXX.csv
f-100713 XXX.csv
f-100713 XXX.csv
f-100713 XXX.csv
f-100713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-110713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
f-120713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-100713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-110713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv
r-120713 XXX.csv


I would like to import all files into a workbook based on 2 criteria ( r or f) and the the number that follows.
So that (for example) all the files that contain f-100713 are saved in the same workbook.
...and all the files that contain r-100713 are saved in the same workbook.

In my example of files I would end up with 6 workbooks f-100713, f-110713, f-120713, r-100713, r-110713, r-120713.
The "XXX" part of the filename can be almost anything so I presume I would need some kind of wildcard.
I am unsure how I can achieve this.

Any assistance appreciated.

Thanks!