[xsl] XSLT1.0 and wildcards

Hi All
         I am working with XSLT1.0. I am having a scenario where i get
address data from source side and i have to split it ot three fields.

For example The address line is like this: melkweg 51a.

This means I have to map this like this:  street = melkweg, number = 51,
extension = a
    I wanted to use the  'substring-before' function to filter out the
street, and 'substring-after' function to filter out the extension. I could
use the number 51 for this but that's only the case for this line. Can i use
some kind of wildcard character say '*' that defines that It just has to be
a number.
Are there such wildcards, and/or is there a better way to do this?

Thanks
Pan