XSL Newbie seeks help

HI,
I searched the archives and must admit I am not sure if
I found what I needed, as a lot of what I see is all
new to me.

I am successfully applying a very basic XSL sheet to an
XML document using <xsl:template match="Field"> against
an XML document which has multiple "Field" nodes but
with different names, like this:

<Field FieldName="DOCID">abc1223</Field>
<Field FieldName="COUNTRY">USA</Field>
<Field FieldName="COUNTRY">Canada</Field>

This works great, but as you may have noticed, some
fields have the same FieldName attribute, and sometimes
there can be a dozen countries, and this make my
transformed document (HTML table) much longer as it
creates a row for each COUNTRY entry.

How would I evaluate that there is more than one
occurance of the Field/FieldName combination so that I
can create a concatenated list of contries so as to
display them all on only one row?

Any help appreciated.

Jim