Entering pauses in a phone number string for a contact

When creating a phone number for a contact, is it possible to insert a "pause" at various points in the string of numbers?

This is useful when I call my office voicemail from my cell phone. I have to pause a few seconds while the voicemail service answers, then enter my password and mailbox number. My Motorola cell phone allows me to program the phone number to dial, add a few pauses, then the password, etc. So when I call my voicemail, the phone does all the dialing for me while I keep my eye on the road.

Does the iPhone offer a similar way to create "pauses" in a contact's phone number? Otherwise I'll find myself trying to enter my password and mailbox number (16 digits altogether) manually each time -- a hazard while driving, and wholly undesirable.

Is there a work-around? For example, can I make one contact entry for the phone number, and another "contact" for the password and mailbox number? That would only work if I could dial that second contact while on the line with the first? From what I've seen, this wouldn't work.

I welcome any assistance with this.