Thanks for the awesome help Navi. I was able to use your example to get my event to occur. A quick note for anyone else is that I had to manually change my layout file to use LineEditExtended instead of LineEdit.
I should have been a bit more clear on my full goal as I still need a bit more help. What I've got is a LineEdit that continuously scrolls as external data is fed into it. I want to stop the field from scrolling while the user has clicked the scrollbar, and then resume scrolling once it's released. I'm thinking I need a whenleftup event but there isn't one available. There is a virtual void LeftUp but I don't know how I might make that work.
Basically I'm looking for exactly what you gave me plus an event on the leftup as well.