Using 'lower-case' in XPath Query

Hi!

I'm not sure if this is the right forum but I'll try anyway and hope for the best!

I'm having a problem using the 'cotains' XPath string-function and the problem is that it is case-sensitive. I thought of using the 'lower-case' XPath stringfunction in order to compare attribute values converted to lower case against a search pattern which is also converted to lower-case. The problem is that I don't know what I need to do in order to use the lower-case function from within my XPath query. An example:

Instead of using this:
//WORDSET[contains(./PHRASE/@text, 'string')]

I'd like to do this:
//WORDSET[contains(lower-case(./PHRASE/@text), string)]

Is this possible and how

Thanks for your help!
/Peter