You have to press the button once for each spell you want to cast, but you can use a castsequence macro:
Code:
/castsequence Some Spell, Other Spell, Last Spell
You can’t set special targets for some spells in a castsequence, though. If you can explain more about what you want to do, I might be able to give you a better example.
There’s a lot of good explanations and examples for making macros here:
http://www.wowpedia.org/Making_a_macro