extracting substring from a string

i am trying to get a substring using vbscript and not able to get it.

Here is the whole string/

varWI=  Work item W396364-01FEB18 created. I need to extract just the number W396364-01FEB18

using the below but it is not working

start=$$eval varWI.substring(varWI.indexOf("W"))

end = varWI.indexOf((" c"),start))

Number = varWI.substring(start,end)