Hello again,
Updating as promised...


With the 'Use wildcards' box checked, I tried applying
Find = (\[[0-9]{2}:[0-9]{2}:[0-9]{2}\])^32([A-Z]{2})^32
Replace = \1^t\2^t
to a representative file but, alas, the search returned "0 replacements"
However, I'm not discouraged.
Your first reply to my posted question reinforce the direction that my ongoing efforts /experiments have been taking. Indeed, I have constructed a multi-step procedure that is doing the job - albeit in a way that lacks the elegance of a carefully crafted, single search string. (Something which your model solution suggests can be achieved through deft design - not to mention experience.)
Moreover, your 'eye-opener' prompted me to discover a web article by Graham Mayor: "Finding and replacing characters using wildcards" http://word.mvps.org/FAQs/General/UsingWildcards.htm which provides a concise overview of Theory and Practice.
Thanks again. I'll be back!
PF