I would like to find strings that exclude a short list of words - namely the brand names

So the macro would find anything except: apple, sony, asus and for those string(s) if there's any spaces add an _

The sample below shows several strings per row. All strings are contained within one cell. For example "Apple tom jones 456 1/12/12" is all contained within cell a1 & "Apple steve smith 525 2/12/12" within a2 etc. Numbers should be excluded from the search.

Below is the brand name, customer name, area code, date of purchase

Sample Data:
Apple tom jones 456 1/12/12
Apple steve smith 525 2/12/12
Sony JOE william johnson 262 5/12/12
Asus Carla Fausto 525 4/12/12

Desired Output:
Apple tom_jones 456 1/12/12
Apple steve_smith 525 2/12/12
Sony JOE_william_johnson 262 5/12/12
Asus Carla_Fausto 525 4/12/

any insight is appreciated thank you!