Converion based upon my old Deckel Mill

[John11668]

Have had an old Deckel FP 1 mill in my shop for years and it still does good work. (Pics attached ) but I have been tempted for some time to use it as the base for a CNC conversion

Rather than interfere with a classic, I have planted an Axminster compound table onto it https://www.axminstertools.com/axmin...d-table-400385 and converted that table with stepper motors and Chinese ballscrews.
I built my panel and with all sorts of problems along the way. I then downloaded a licensed version of Mach 3 and with a few more problems managed to get the table moving in X Y plane. That is a very abridged version of what went on, but with a simple routine I managed to cut a pocket.

Clearly I needed a Z axis ( not easy on a Deckel where the usual Z motion lifts the whole table)
The quill has very little backlash, so I have added a Heath Robinson drive to give me the Z motion and it all seems to work fine
https://www.youtube.com/watch?v=lpDV7Lj5mTY
Sooooohh, I know this is a rough project, but If I can get an understanding of the processes then I will move to building something a little more refined .

So I now want to make the machine loop through the same repeated routine to a given depth.
I am told that IF and GOTO instructions are not supported by Mach3 and if I try to use a parameter to define the depth , increased at the start of a subroutine I get a vague error message which tells me it does not understand the word .

How would others program this to cut progressively down to say a depth of 6mm
Please go easy on me . I am a total newbie and struggling with the tutorial manuals .