Here is a quick solution, should get you passed this hurdle.

😎

USE tempdb;

GO

DECLARE @XML_ID INT;

DECLARE @FILE_NAME VARCHAR(255);

SET @XML_ID = 2;

SET @FILE_NAME = 'text_file.txt';

DECLARE @TXML XML ;

DECLARE @XML_TABLE TABLE (XML_ID INT IDENTITY(1,1) NOT NULL,TXML XML NOT NULL);

SET @TXML = '<custid>1234</custid>

<procflag>P</procflag>

<txtfilename>file1.pdf_file2.txt</txtfilename>

<filename>ST_1234_go.ps</filename>

<stmt>987654321</stmt>

<loc>2</loc>

<doc>100</doc>

<acctnum />

<deliverymethod>M</deliverymethod>

<batchid>456321</batchid>'

INSERT INTO @XML_TABLE (TXML) VALUES (@TXML);

INSERT INTO @XML_TABLE (TXML) VALUES (@TXML);

INSERT INTO @XML_TABLE (TXML) VALUES (@TXML);

SELECT * FROM @XML_TABLE

UPDATE @XML_TABLE

SET TXML.modify('replace value of (/txtfilename[1]/text())[1]

with sql:variable("@FILE_NAME")')

WHERE XML_ID = @XML_ID

SELECT * FROM @XML_TABLE