The only guide that we have for this is an older one that I feel is too outdated to be useful to you in your current setup.
The idea is pretty straight forward though. If you are wanting to tax only for FL then you need to first set a session variable if the user selects FL. In this session variable you can set it to any value you would like.
The next part is to add in your tax rule, in here when you set it up you will select based on session variable exists, then select the newly created session, then add in another condition to the trigger that says if session variable has a particular value, then enter the value that you assigned to the variable.
This should allow you to charge the tax rate for your state, just use based on cart subtotal and times 0.07. Let me know if you have any trouble with this and post back with a copy of your confirm page and we can show you how this needs to be setup.
