can you pleas tell if there is button to pop the trunk

The only ways to open the trunk I can find are, with the key, and by the keyless remote in you have one. This is according to the owners manual. If you need an owners manual you can download one free at: http://www.autousermanual.com/view/buick/regal/

The only trunk release is on the key fob or use the key in the trunk lock

For the 99 GSE BUICK REGAL. I went inside the trunk threw the back seat an pulled the cable attached to the lock. After hearing a click. I pulled the trunk open from the outside. Very simple. Unlike all the complicated ways I read about.