I read about this feature in link below and looked useful to have on hand, it will be added to UCCNC in the very near future but in the mean time can you try it here.
viewtopic.php?f=2&t=1682
By adding a forward slash to the beginning of a gcode line this gives you the option to block line if needed with macro #4545, and unblock it with
macro#4646. If you want to add a button to use macro's you will have to change the macro numbering, I suggest the multiple macro plugin that could be found in toolbox forum section.