input text: advance to the next field automatically?

I'm trying to simulate how dates work in an web app.

It has --/--/---- before you type.

Type month in numbers after entering 2 numbers, it automatically advances to day area and then to year.

I'm thinking having input text fields and limit to 2 characters and numbers for the month and date. 4 for year. How do I do so it automatically moves to the dates after finishing the month without using tab or clicking on the field?

Thanks,