Need to add sentences to Description metadata without deleting current description

[ctc14]

hello! I am doing some work where I am going through a large archive and updating/editing the metadata. I've figured out how to do many of the things I need to quickly, but I can't solve my problem with editing the description metadata. Many of the photo files already have a description in them, which I would like to keep, but I need to add a sentence or two after the description that is already there (it might be a folder with 30 files, each with a different description that describes something specific about the photo, and I want to add the same sentences to all 30 files' descriptions without deleting the original, unique description in each file). It would save me a lot of time since right now I have to just click on each file separately and paste the extra sentences in manually. I thought the 'append metadata' feature was going to help, but it doesn't seem to work? When I create a template (with just the sentences I want to add in the description) and then select the files and 'append metadata', nothing happens. 

Is there a way to do this, or am I stuck entering this stuff manually? thanks in advance!

[Lumigraphics]

You would have to write a script that would read the description, add to it, then write the data back out to the file.

[SherrieLB]

It would seem to me too that's what the "append" command should do. I would also like to add to descriptions by creating a template with additional description then appending to the description field. It's been working that way for adding keywords but not description.  

[Lumigraphics]

Append won't replace what is there, only add data to empty namespaces.

[SherrieLB]

Hi, thank you. I don't want to replace what is there, I want to add to (aka append) the current description but that only appears to work in the keyword field as I have been able to successfully add additional keywords to those that are already in that field. Can't seem to add to the description field this way though. Wondering whether anyone had experienced this or had a solution (ideally that doesn't involve writing or adding script). Thanks again. 

[Lumigraphics]

Some XMP fields can have data appended but most can't. You can't do this without reading what is there and adding to it, which will require scripting.