To extract the random text from your application first you need to be sure that Test Studio finds
the element containing that text by "id" or other non randomly changed element's attribute.
Next step is to create an extraction step
in your test to get the randomly generated text.
After that - add a coded step
, where you can place C# code that process the sting you have. For example if you want to split strings in C# you may refer to this article
. For saving data in Excel format you may search in google for how to
and use it also in a coded step.
Let me know if that helps.