Many thanks for the guidance & help I was able to modify the navigation exactly as I wanted. I'm very interested in how this was done and I have a number of questions! Let me just start with one: it seems clear that the set of commands you provided for Menu PGC 6 are the key to going to the relevant chapters menu when using the 'menu' button.

What I'm not really clear about is what these commands mean. It does seem that they fall into groups of three and that these groups relate to each of the menu chapters. The 'if (R[0] != n) goto line n' commands seem to be 'skipping' ones - if something is not equal to a given number, then jump to a given line (which then has a similar command).

I wonder if you can explain what the typical group of commands that follows actually means (what their effects are)? I notice that in the command R[1] = n the value for 'n' ascends from 1 to 3 for each group.

if (R[0] != 1) goto line 5
R[1] = 1
Link PGC 2