FW: Trying to translate code with specific values into

I am trying to translate code using specific values into code that uses
variables to represent those values.

Here is an XML example:
<chunk km="Ch">
<table-wrapper km="Ch.1.Ta.A">
.....
</table-wrapper>
<table-wrapper km="Ch.1.Ta.A">
.....
</table-wrapper>
<table-wrapper km="Ch.1.Ta.A">
.....
</table-wrapper>
</chunk>

The following code counts all the table-wrapper elements with a km
attribute that ends in Ta.A that are inside of this chunk element where
the km attribute value is Ch.

<xsl:value-of select="count(preceding::table-wrapper[ends-with(@km,
'Ta.A')][ancestor::chunk[@km='Ch']])+1"/>
This example works perfectly.

But when I try to represent the working code above with variables, I get
an error:
<xsl:value-of
select="count(preceding::*[name()=$counterElement[ends-with(@*[name()=$c
ounterAttName],$counterAttValue)]][ancestor::*[name()=$containerElement[
@*[name()=$containerAttName]=$containerAttValue]]])+1"/>

  Here is the error:

XPTY0020: The context item for axis step attribute::attribute() is not a
node

Does anyone have an idea of what I'm doing wrong?

Thanks.
Emily