在VBA (excel)中返回regex匹配

I am trying to write a function for excel 2010 that will take a cell of unstructured text, look for something called an sdi value and, if found, return that number. The sdi value will appear as sdi ####. What I want is to return sdi and the sepecific numbers that follow it, so if the cell contains "some text sdi 1234 some more text" the function will return sdi 1234. I am trying to write a function for excel 2010