for-each inside an attribute value template

I need to pass parameters in a URL like: <a 
href="page.jsp?param1=x&param2=y" />
The number of parameters is unknown.

I want to call the parameters using something like xsl:for-each, but 
that won't work inside the href attribute. I'm wondering what approach 
to take. I've tried to escape the <a href=" part, but then it isn't 
treated as html anymore. Is there something similar to a for-each inside 
an attribute value template?
I've found something about <xsl:result-document href="{$xyz}"> but am 
not sure whether this can solve my problem or is the right direction to 
look.
Roger