SurveyToGo fully supports scripting and usage of entrance rules (Skip Rules).
From the simplest ones, to the most complicated.

An entrance rule is a script that runs before a question is entered and decides whether this question will be asked or skipped.
If the script is valid, the question will be asked, if not, it would skip it.

Write your Entrance Rule.

You can find the entrance rule text box in each questions ‘Rules’ tab:

Now we can add an entrance rule as we wish.
For example:

This rule, will show the specific question, only if the answer of question 5 is answer 2.

You can add much more complicated rules and even use functions.
Further more, you can use the ‘Create Rule’ Wizard, however, it is more limited then writing your script on your own.

That’s it!

Important Note

Writing Entrance Rules that are very long could result in a "Stack Overflow" exception and failure to load the survey.

Please refrain from writing Entrance Rules that are too long. Entrance Rules are designed to be relatively short. 

If you need to write complex conditions, it is recommended that you write a new function in the Advanced Scripts and use it in the Entrance Rule.

If you want to learn about writing functions in the Advanced Scripts, please refer to this guide:

http://support.dooblo.net/entries/23537367-How-To-use-functions-across-a-script-using-the-Advanced-Scripts-section