Your question is answered by having a look at the PR card renewal instruction guide found here: http://www.cic.gc.ca/english/information/applications/prcard.asp
On the application form itself, it just asks you to explain if you have been outside Canada more than 1095 days and one of the options is this one:
Absence while employed by a Canadian business
However, when you read the instruction guide at http://www.cic.gc.ca/english/information/applications/guides/5445ETOC.asp you will find this:
OPTION 2. Employment outside Canada
You may count each day you were employed outside Canada if your employment meets the following requirements:
* you are an employee of, or under contract to, a Canadian business or the public service of Canada or of a province or territory and
*as a term of your employment or contract, you are assigned on a full-time basis to:
- a position outside Canada
- an affiliated enterprise outside Canada or
- a client of the Canadian business or the public service outside Canada
You can also find this here: http://www.cic.gc.ca/english/resources/manuals/op/op10-eng.pdf on page 11
6.5. Employment outside of Canada
The Regulations enable permanent residents to comply with the residency obligations while working abroad, provided that:
they are under contract to or are full-time employees of a Canadian business or in the public service, where the assignment is controlled from the head office of a Canadian business or public institution in Canada; and
they are assigned on a full-time basis as a term of their employment or contract to a position outside Canada with that business, an affiliated enterprise or a client.
So if you are not assigned on a full-time basis to a position outside Canada, just travelling for business occasionally, your days outside do not count towards the PR residency obligation. Even if it did, it may also be questioned whether your employer truly counts as a Canadian business. If this is a problem, you may want to ask your employer to transfer you to a position where business trips are not required or look for another job.