temporary work offsets. external offset or something else?

#!/usr/bin/tclsh

# EDIT here to set ::the_pin_name as required:
set ::the_pin_name_1   motion.analog-in-00
set ::default_value_x  0
set ::the_pin_name_2   motion.analog-in-01
set ::default_value_y  0
set ::the_pin_name_3   motion.analog-in-02
set ::default_value_z  0

# Note: This file must:
#    have execute permissions (chmod +x this_file_name)
#    be located according to rules for user M codes
#    exist before starting LinuxCNC

#------------------------------------------------------------------
set ::prog [file tail $::argv0]
set ::value_x $::default_value_x
set ::value_y $::default_value_y
set ::value_z $::default_value_z

package require Hal
package require Tk

proc go {} {
  if [catch {
    puts "$::prog:$::the_pin_name_1 before: [hal getp $::the_pin_name_1]"
    hal setp $::the_pin_name_1 $::value_x
    puts "$::prog:$::the_pin_name_1  after: [hal getp $::the_pin_name_1]"
    puts "$::prog:$::the_pin_name_2 before: [hal getp $::the_pin_name_2]"
    hal setp $::the_pin_name_2 $::value_y
    puts "$::prog:$::the_pin_name_2  after: [hal getp $::the_pin_name_2]"
    puts "$::prog:$::the_pin_name_3 before: [hal getp $::the_pin_name_3]"
    hal setp $::the_pin_name_3 $::value_z
    puts "$::prog:$::the_pin_name_3  after: [hal getp $::the_pin_name_3]"
    hal setp $::the_pin_name_3 $::value_z
  } msg ] {
    set ::value_x "FIXME"
    set ::value_y "FIXME"
    set ::value_z "FIXME"
    popup "ERROR\n\n$msg"
  } else {
    exit 0
  }
}
proc abort {} {
  popup "Aborting Gcode program"
  exit 1
}
proc err_exit {msg} {
  popup $msg
  exit 1
}
proc popup {msg} {
  puts stderr "$::prog: $msg"
  tk_messageBox \
    -title "$::prog Set Offset" \
    -type ok \
    -message "$msg"
}

wm title . "$::prog Set Offset"
wm protocol . WM_DELETE_WINDOW  {puts "$::prog: window close disallowed"}
pack [label .l1 -text "X:"] -side left
pack [entry .e1 -textvar ::value_x] -side left
pack [label .l2 -text "Y:"] -side left
pack [entry .e2 -textvar ::value_y] -side left
pack [label .l3 -text "Z:"] -side left
pack [entry .e3 -textvar ::value_z] -side left
bind .e1 <Return> go
pack [button .b -text Go -command go] -side left
pack [button .a -text Abort -command abort] -side left

o<401remap> sub
 ; open user input popup
 M141
 ; update motion.analog pins
 M66 E0 L0
 ; set current work offset
 G10 L2 P0 X#<_hal[motion.analog-in-00]> Y#<_hal[motion.analog-in-01]> Z#<_hal[motion.analog-in-02]>
o<401remap> endsub

[RS274NGC]
    USER_M_PATH = ./mcodes
SUBROUTINE_PATH = ./remap_subs
   HAL_PIN_VARS = 1
          REMAP = M401  modalgroup=10  ngc=401remap

#!/usr/bin/python3
import linuxcnc
import tkinter as tk
from tkinter import Tk, X, BOTH, LEFT
from tkinter import ttk
from tkinter.ttk import Frame, Label, Entry, Button

# add/remove the entries needed
entry_list = ('X','Y','Z')

class SimpleDialog(Frame):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.master.title("Enter Offset    ")
        self.pack(fill=BOTH, expand=True)
        self.entries = []
        for entry in entry_list:
            self.e = self.createEntry(entry)
            self.entries.append(self.e)
        self.label_error = ttk.Label(self, foreground='red')
        self.label_error.pack(fill=X, padx=5, expand=True)
        frame_last = Frame(self)
        frame_last.pack(fill=X)
        self.btn = Button(frame_last, text="Set", command=self.onSubmit)
        self.btn.pack(padx=5, pady=5)
        self.btn.bind('<Return>', self.onSubmit)

    def createEntry(self, entry):
        frame = Frame(self)
        frame.pack(fill=X)
        lbl = Label(frame, text=entry+":", width=4)
        lbl.pack(side=LEFT, padx=5, pady=2)
        self.vcmd = (self.register(self.validate), '%P', '%W')
        self.entry = Entry(frame)
        self.entry.insert(0, '0')
        self.entry.config(validate='focusout', validatecommand=self.vcmd)
        self.entry.pack(fill=X, padx=5, expand=True)
        return self.entry

    def show_message(self, w, error='', color='black'):
        color_state = []
        self.label_error['text'] = error
        for i in range(len(self.entries)):
            if w == str(self.entries[i]):
                self.entries[i]['foreground'] = color
            color_state.append(str(self.entries[i].cget('foreground')))
        if 'red' in color_state:    
            self.btn.configure(state="disabled")
        else:
            self.btn.configure(state="normal")

    def validate(self, value, w):
        try:
            result = float(value)
            self.show_message(w)
            return True
        except ValueError:
            self.show_message(w, 'Invalid entry.', 'red')
            return False

    def onSubmit(self, *args):
        value1 = float(self.entries[0].get())
        value2 = float(self.entries[1].get())
        value3 = float(self.entries[2].get())
        # Get rid of the error message if the user clicks the
        # close icon instead of the submit button
        try:
            root.destroy()
        except:
            pass
        c = linuxcnc.command()
        c.mdi('G10 L2 P0 X%f Y%f Z%f ' % (value1, value2, value3))
        self.quit()

# This part triggers the dialog
root = Tk()
# the more entries in the list the longer the window needs to be
l = len(entry_list)
root.geometry("250x" + str(l*22+60) + "+300+300")
app = SimpleDialog()
root.mainloop()