Creating an XPath Expression in SharePoint's "Add Formula Column" based on meta data -

ok,

so first post stack overflow, , did search , couldn't find looking regard question (although might terrible @ searching). essentially, first pass @ xpath expressions , having tough time creating if/else statement.

i have dwvp displaying list of documents document library on separate site. have column notes whom document checked-out (if checked-out), , if document checked out, have conditional formatting highlight row.

all far. have list of documents have bunch of meta data , 1 or 2 of rows in list highlighted yellow because checked-out, , users name listed in "@checkedouttouser" column.

my issue want create column (i'm assuming formula column) within dvwp display link source document library (specifically view enabled filters content "checked out to" [me], that's no issue) if column "@checkedouttouser" has in it.

my thought process here new formula column check see if anything written (or alternatively not written) in column, , if create link says "check-in document". if @ dvwp, see yellow row indicates document has been checked out, , since yellow , since checked out, right-hand formula column show link says "check-in document".

i have never written xpath expression before, got somewhere following expression:

if /@checkedouttouser!=" ",

i have feeling start that?

what expression like?!

not quite sure want do, little bit of xslt , xml help

<xsl:if test="@checkedouttouser"><span>add content<span></xsl:if> 

if need display underlying xml page, deprecated tag

<xmp><xsl:copy-of select="." /></xmp>

will trick.