Is this for one or a few buttons? Or many buttons over many pages? If it is just a few, then in Indesign, you can set a button action to go to a destination (in your case 2 pages ahead). Copy buttons, and modify as necessary.
Buttons can jump to Text Anchors placed anywhere else in the document.
There are plenty of PDF button features that can't be assigned in InDesign, but can be added in Acrobat, post-export.
I don't think the script would be hard to write for that...
Could be, but you don't need a custom script. Just use the Go To a Page View item on the Button Properties Actions tab in Acrobat.
...I can't figure out how to attach a script/action to a button...