concat string to an variable name

Hi List,

I have variables like this: (and many more)
<xsl:variable name="HE01_1">-30 min.</xsl:variable>
<xsl:variable name="HE02_1">08:00</xsl:variable>
...
<xsl:variable name="HE01_2">Day 1, 08:00</xsl:variable>
...
<xsl:variable name="HE11_8">Day 11, 08:00</xsl:variable>

At runtime I want to return one of this variables. Which variable is the
right is determined on the basis two values.
1. The Element <PRINTTYP/> which has values like 'HE01', 'HE02' ans so on.
2. A other Element <ROW/> which has values like '1', '2' ans so on.


I concat both values like:
<xsl:value-of selct="concat($Printtyp, '_', $Row)"/>

to create a string matching an variable name like 'HE01_1'.

My question now is, how can I select the variable whish name matches the
createt string? 
Is this possible?

thanks!!!