Function to return number

I am trying to create a function that  return the number part within / / from a url if exist:
For exmple:
http://www.mydomain.com/Mobile_Exec/1234/Orange_revamps_business_website.aspx SHOULD RETURN "\1234\"
http://www.mydomain.com/News/Orange_revamps_business_website.aspx    SHOULD RETURN "\\"
http://www.mydomain.com/News/Features/627362/Orange_revamps_business_website.aspx SHOULD RETURN "\627362\"


I prefer if possible to use regular expression. Any help would be really appreciated.
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