Removing product taglines

[DoubleD82]

Hi,

I have a requirement to update product tag lines based on their stock availability.

The requirement is:

• If the product has stock available, a tag "nextdaydelivery" needs to be added
• If there is no stock available, a tag "nonextdaydelivery" needs to be added
• If it previously had either of these 2 tags added, said tag needs to be changed based on availability
• Other tags must not be edited in any way

It's easy enough to add tag lines, but how do I go about either updating or deleting tag lines?

Does someone have an example of this? Even if the example is a category example.