function Get_Closest_PT(pObject) -- not tested, it should work I guess, don't forget to replace 'PT_Name_Here' with PT's name from Leveleditor. Every team have a different PT name.
local closest = 1000
for i,v in ipairs(Get_All_Objects()) do
 if Get_Preset_Name == "PT_Name_Here" and Get_Distance(Get_Position(pObject), Get_Position(v)) < closest then
   closest=Get_Distance(Get_Position(pObject), Get_Position(v))
 end
end
 return closest
end