Import text into existing slides

I am using PowerPoint 2007 to modify an existing PowerPoint show of
300 slides with photos and notes on each one.
I want to add text titles and subtitles from a Word outline document
into placeholders on each slide without affecting the existing photos
or notes.

"Import from Outline" from Word seems to only insert new slides in
sequence but doesn't import into existing.slides.
I've tried using Shyam Pillai's "Transfer Title Slides" but
unfortunately it only transfers titles without subtitles.
I've been using keystroke macro software as a work-around but it's
problematic.

Is there a way to do this across the whole show other slide-by-slide
cut & paste?

Thank you for any suggestions!