Replacing an apostrophe in a string

I have to escape several characters, one of which is an apostrophe, in strings
that I am writing out to a DOJO script. I've tried everything I can think of
but can't get the apostrophe replace working.

Here's of few of the replaces I've tried: (note that all of the double and
single quotes are the regular keyboard characters - outlook has altered them
below)

<xsl:variable name="newString" select="replace(oldString, '(['])', 'XXX')"/>

<xsl:variable name="newString" select="replace(oldString, '&apos;', 'XXX')"/>

<xsl:variable name="newString" select="replace(oldString, '''', 'XXX')"/>

How can I get this to work?

For the examples
oldString = that specifies condition's to be evaluated

newString should be = that specifies conditionXXXs to be evaluated

Thanks,
  Craig