HTML Payment Drop-Down Box

Hi, I don't have much experience with this kind of thing so I thought I'd ask.

I am integrating a new payment provider into my site (an Australian company called Paymate, which are like Paypal but without the total lack of service and BS you have to go through with Paypal) and I's like to have a drop-down box with a few services which my customers can then click "buy" and they will be directed to the payment page of the item that's been selected.

So, does anyone know the code of how I would do this? I know that each URL has to be a different "option" in the code itself, though I don't know exactly how to make it work. Little help?

Thanks.