Indeed, you can use a trigger to accomplish your goal.
The trigger will be a "form-in" trigger with a "path" value of "client".
You'll need to learn to work with the Perforce command line, and with the simple text file format that Perforce uses for workspace specs.
You should have a look at this related question: How to set defaults for perforce client specs
And you can find documentation and examples in the Perforce manuals here: http://www.perforce.com/perforce/doc.current/manuals/p4sag/chapter.scripting.html
Here's another older document with some good background material: http://www.perforce.com/sites/default/files/writing-triggers-paper_0.pdf
After you've read all that material, set up a test server to use for developing your triggers, and tried writing some triggers yourself, you'll probably have some additional questions to ask about the details, but your proposed trigger is simple enough that you'll probably be able to figure it out with some experimentation once you've looked at these examples.