Text replacement

Hello,

I have a question concerning XSL and text replacement. I have the
following simple XML structure:
<data>
<element>&#345;&#123;&#453;</element>
</data>

Now I want to transform this to:
<data>
<element>+++</element>
</data>

So what I want to do is to replace parts of the form &#<number>; with a
special character (e.g. +). Of course I want to do this in attribute
values too and it might be possible that a string is mixed:
&#345;ab&#123;cdef&#453; will be transformed to +ab+cdef+. Is it
possible to do this in XSL with
a) no self written extension (only standards)
b) the usage of XSL 1.0 (no absolute necessary)?

Regards
Markus

.