Hmmm, I see what you mean Bill!  .dat is a catch-all format that's can be defined for any specific program, but they are often readable by a text editor or opened as a csv.  But not in this case clearly!!  Have you done a search on screw mapping here?  I'm sure that I've seen something somewhere on using in-built features to move the axis and capture the DRO value.

I have seen everything on this site and spent hours looking on the web, not much info on the subject.
it's a shame that there isn't a oembutton for adding a data point to the file with a macro. There is for
bring up the window but that's it.

I had a sudden thought - another .dat file in mach3 is the tool table.  There are a couple of macros around to export and import the tool table, I have versions by Rimmel that work very well.  You might see if they could at least be modified to work with the screw map file?  I attach copies, for more info try searching for "tool table export" on here?

Thank you John, I will investigate this tonight, I just started to learn about macro's for spreadsheets and mach3
a couple of weeks ago so I know just enough to be dangerous.