Do you chat with them while they are at the office? Is the software company-sponsored, or generic AOL/Yahoo/MSN stuff? Is there video capabilities?

I am in a similar situation. I tell her sexy stories online while she is at work. She gets all wired up and sometimes brings herself of while sitting at her desk. She works in a "cube farm," so there's some risk of being walked in on.

You could try "assigning" them to wear specific outits that are more showy than they are accustomed. Something along the lines of a push-up bra, a shorter skirt, plunging necklines. Start with one item, then expand. See how far you can go with it.