Find certain letters at beginning of textbox?

[Akskater1000]

I wanted to make an application in flash that switches the first letters of two words. (I know it's a stupid idea, just wanted to show my dad I could...) Okay. I have two text boxes, and when I hit the "swap" button, I want it to switch the first two letters of the two words and put it in a third text box. If it is a consonant pair like sh, ch, st, cr... I want it to move both of the letters. I have a lot of experience in Actionscript 2.0 but none in 3.0. Any help?

Edit: I am sorry if this has been posted before. If it has please direct me to the topic and you can delete this topic.