For 2008 NEC, Article 334.80 for Ampacity of NM cable states.
Where more than two NM cables containing two or more current-carrying conductors installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be fire- or draft- stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2) shall not apply.
Where more than two NM cables containing two or more current-carrying conductorsare installed in contact with thermal insulation without spacingbetween cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).
Table 310.15(B)(2)(a) Adjustment Factors for More Than
Three Current-Carrying Conductors in a Raceway or Cable
Number of ---------------- Percent of Values in Tables
Current-Carrying ------------- 310.16 through 310.19
Conductors ---------------- Adjusted for Ambient
--------------------------- Temperature if Necessary
_________________________________________________
4 - 6 ______________________80
7 - 9 ______________________70
10 -20______________________50
21 -30______________________45
31 -40 _____________________40
41 and above__________________35
_________________________________________________
Being that you can use the 90 degree column for derating purpoes its not usually a problem with #14,#12,and #10 conductors untill you pass 9 current carrying conductors.
That would make 4 cables = to 8 current carrying conductors since the exception doesnt apply.
or you could have one of the cables be a three wire then 4 would equal 9 current carrying conductors and would be ok.
Sorry havent figured out how to get the Tables to look right.