just create a new list for the companies and use this new list as the source for the company drop down:

Data Range
A
B
C
1
Apple
Brad Pitt
Apple
2
Apple
Robert de Niro
Microsoft
3
Apple
Kevin Spacey
ATT
4
Apple
Seth Rogan
Cisco
5
Microsoft
Julia Roberts
6
Microsoft
Jennifer Lawrence
7
Microsoft
Scarlet Johanson
8
ATT
Al Pacino
9
ATT
Arnold Schwarzenegger
10
ATT
Joe Pesci
11
ATT
John Cusack
12
Cisco
Demi Moore
13
Cisco
Mila Kunis