Remap M6 tool setter

hello guys,
i have 5 axis milling cnc machine and i want to use tool setter to measure the tool length, i am using versa probe and m6 remap ngc code as given from qt dragon documentation  (  linuxcnc.org/docs/html/gui/qtdragon.html#_auto_tool_measurement ) , what i expected to be done is as follows:
1- Manual Change tool
2- probe down to Tool setter
3- calculate the tool length
4- update the tool table

what qt dragon do is that it needs the probe height and workpiece height  and calculate the distance between them to be able to set the the tool length by using this equation (Probe result - diff between probe height and workpiece height), from my knowledge in tool length meseurment there must be tool length reference and the tool length is the diff between tool reference length and the tool length measured. i want to calculate the actual tool length.
can someone help me it has been 2 weeks stuck in this problem !!!

Qtdragon/Gmoccapy's Auto tool measure, does not use the tool table fir Z length. It's intended for non repeatable length tool holders.

This (rough) video shows the basic principle:


For more standard tool length probing, the master branch unlocks a couple more buttons in Versa probe that updates the tool table. It's only lightly tested.
talked about here:
forum.linuxcnc.org/qtvcp/51138-qtdragonh...maker-space?start=20