Searching all Stored Procedures for an update of a specific column
Do you have many procedures that getting the rough net and then eliminating any false positives manually would be extremely objectionable?

SELECT s.name, p.name, m.definition
  FROM sys.procedures AS p
  INNER JOIN sys.sql_modules AS m
  ON p.[object_id] = m.[object_id]
  INNER JOIN sys.schemas AS s
  ON p.[schema_id] = s.[schema_id]
WHERE LOWER(m.definition) LIKE '%update%transaction%terminalid%'
   OR LOWER(m.definition) LIKE '%update%terminalid%transaction%'
   OR LOWER(m.definition) LIKE '%with%transaction%update%terminalid%';


The last case to cover this form:

;WITH x AS (SELECT ... FROM dbo.Transaction)
UPDATE x SET TerminalID = ... FROM x INNER JOIN ...;


I don't know how much more reliable a "better" RegEx could be at identifying only those that truly update that column, and never identifying a false positive. In fact any real update statement that matched the above expressions (or any RegEx expression you would be likely to cook up initially) could be embedded in a comment or a string.

I'd suggest start simple. If the above yields way too many false positives then get more precise.