Move Sop in Panel , Adding Values to Existing position and hold

I am thinking of moving SOPs in the panel with mouse,
how do you add value to existing position of SOP to follow mouse, and hold the value until you move it again?
from panel uv to SOP’s tx ty, tz ?

i managed to get the sop to convert to TOP then chop to get the uv position, but have yet to figure out the other direction,

grateful for any ideas