OK,
I have it working.
For the Emco5cnc ATC this macro now works.

First of all one has to Home the ATC in Mach3 Manual screen >> Home All.
Then , in Mach3 Auto, load the G-code to be executed.

The macro looks if the Homing has been done and sets a two variables.
One that homing has been done and one to make sure that Mach3 knows that the ATC homing position
is the Tool #1 position.
The hint to use SetVar helped me a lot.

Jos


' Based on Boxford 160TCL Toolchanger Macro.
' Modified for the EMCO5cnc Automatic Tool Changer.
' ATC has a steppermotor and an optical slot @ INPUT1
' Works by turning CW to just past the tool position
' and then CCW into a stop.
' Axis setup as rotary e.g. move 360 = 1 full turn.


If IsLoading() Then
' Do Nothing, program loading
Else

' Dim Variables

Dim Num_Tools As Integer
Dim CW_Steps_Per_Tool As Integer
Dim CCW_Steps As Integer
Dim HoldingDRO As Integer
Dim Requested_Tool As Integer
Dim Current_Tool As Integer
Dim CW_Feed As Integer
Dim CCW_Feed As Integer
Dim moves As Integer
Dim total_move As Integer

' First check if Homing has been done

If GetVar(300) = 1 Then         ' Has homing been done?
  GoTo Main               ' Yes, is Homed, jump to Main
  Else
End If
 
' If Not, check if ATC is homed.

If IsActive(INPUT1) Then              ' Look for ATC Home pulse
    SensorState = "Active"
Else 
  Message " Input 1 is NOT Active, Home first."
  Code "M30"               ' End G-code execution
 End
End If

If SensorState = "Active" Then
    SetVar(300,1)                    'Is Homed
   Setvar(301,1)            'Set Current Tool as #1
End If

Main

' set up some vars

Num_Tools = 6               
CW_Move_Per_Tool = 62          '360/Num_Tools , not used
CCW_Move = 15

Requested_Tool = GetSelectedTool()
Current_Tool = GetVar(301)
CW_Feed = 700   
CCW_Feed = 700
Current_Feed = GetOEMDRO(818)

' start tool change

Message ("Requested Tool No=" & Requested_Tool)

If Requested_Tool > Num_Tools Then
Message "Requested Tool No. too high, program stopped."
Code "M30"
End
End If

If Requested_Tool < 1 Then
Message "Requested Tool No. too low, program stopped."
Code "M30"
End
End If

If Requested_Tool = Current_Tool Then
' do nothing
Else
' lets do some changing
If Requested_Tool > Current_Tool Then moves = Requested_Tool -Current_Tool
If Requested_Tool < Current_Tool Then moves = (Num_Tools - Current_Tool) +Requested_Tool

total_move = (moves * CW_Move_Per_Tool)+(CCW_Move/2)

Code "G91 G94"                'incremental & Feed per minute
Code "G0 A" & total_move               '& "F" & CW_Feed
Code "G0 A" & "-" & CCW_Move            '& "F" & CCW_Feed

While IsMoving()
Wend

SetCurrentTool Requested_Tool
SetVar(301,Requested_Tool)      'Store Current Tool
Code "G90" ' back to absolute movement
Code "F" & Current_Feed
End If
End If

' end of tool change