Can an age derived factor be created to include the upper limit?

I'm not sure if this is the correct place - I wanted to post this in Benefits configuration, but I'm not getting that option.

We have a requirement to allow coverage of a child dependent through the end of the month in which they turn 26. The normal process to have a loss of eligibility life event on their 26th birthday starts the new coverage on the first of the next month, and that works correctly by ending the coverage on the last day of the birthday month. We realized that for the OPEN life event, it is evaluating eligibility on 1/1, and a child who turns 26 on 1/1 is not offered coverage (which makes sense, since they are not UNDER 26), but