Hi Rich. When you refer to your code, do you mean the steps in the sequence or code which is hosted externally to SEQUEmatic?
Assuming this is code hosted elsewhere which will then trigger a webhook request, the answer is that you can reference variables passed from a webhook has parameters by enclosing their name in curly brackets. There is some information here in the docs.
Firstly, the way to name the parameters will depend on your webhook. You should read about the IFTTT webhook trigger and custom webhook trigger for more information. If you can tell me more about the webhook you're using (how does it pass the data - via the URL? as a POST request? is it JSON?) then I can give you more guidance on how to access the data in your sequence.
Once you have determined the correct webhook trigger, you can then access that value by enclosing it in curly brackets. For example, if you passed the current broadband consumption in a parameter named broadband_usage, you would access it as {broadband_usage} in your steps. See below as an example where you can check if {broadband_usage} is greater than 50:
Hopefully these comments help to get you started, and if you can share some more information here I'll be able to provide more specific advice.