How to pass search path as variable and get back node

I have searched FAQ section and can not find answer.
I know it must be there but I can not find it.
Please excuse the redundant question.

Can't figure out how to pass search path as variable and get back node
list.
I get back search string value instead of node list.

<xsl:param name="DATA_REQUEST_NAME"/>  

<xsl:variable name="ftype_search"
select="concat('//JOB_REQUEST/DATA_REQUEST[@NAME=',$DATA_REQUEST_NAME,']/FILE_TYPE')"/>
<xsl:variable name="chosen_ftype" select="$ftype_search"/>

xsl:value-of select="$chosen_ftype"/>

Returns
//JOB_REQUEST/DATA_REQUEST[@NAME=DATAREQUEST4]/FILE_TYPE

How can I get the node list returned instead of the string?



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