How to highlight the current chapter button

[NuPogodi]

Dear DVD-guru,

i've used GUI for DVD Author (GFD) to make simple DVD-menu (root, subs & chapters). The next step was to correct this menu so to highlight the current subtitle button in the subs menu & to highlight the current chapter in the main chapter menu and the related submenues (in my project there are 5 chapter menues: 1-6 (chapter menu), 7-12, 13-18, 19-24 & 25-29).

I've succeeded with the subtitle highlighting in the following waySet gprm(14)=(mov)sprm(2:Sub-picture stream number) # fill user register by the sub stream value
Set gprm(14)+=(add)3 # add 3 to adjust this value to the number corresponding to subtitle buttons
Set gprm(14)*=(mul)1024
(SetHL_BTN) Set Highlighted Button=(mov) gprm(14)

The second task is, though, a bit more difficult. I've tried to read sprm7 and, respectively of this value,
1. to link to corresponding PGCN
2. and to highlight the current chapter button.
Set gprm(14)=(mov)sprm(7:Chapter Number) # fill user register by the chapter value
Set gprm(15)=(mov)0 # another register to store the PGCN i need to link
if (gprm(14)>6) then {Set gprm(15)=(mov)1}
if (gprm(14)>12) then {Set gprm(15)=(mov)2}
if (gprm(14)>18) then {Set gprm(15)=(mov)3}
if (gprm(14)>24) then {Set gprm(15)=(mov)4}
if (gprm(15)==0) then { LinkPGCN PGC 4} # chapter menu entry
if (gprm(15)==1) then { LinkPGCN PGC 5} # chapters 7-12
if (gprm(15)==2) then { LinkPGCN PGC 6} # chapters 13-18
if (gprm(15)==3) then { LinkPGCN PGC 7} # chapters 19-24
if (gprm(15)==4) then { LinkPGCN PGC 8} # chapters 25-29

The above linking to the corresponding PGCN works properly, but i did not succeed to highlight chapter buttons
Set gprm(15) *=(mul) 6
Set gprm(14) -=(sub)gprm(15)
Set gprm(14) *=1024
(SetHL_BTN) =(mov)gprm(14)
If somebody has any ideas how to do it, please, let me know.
Thanks.

[EDIT] Solved... now Chapter Menu redirects user to a PGCN containing the current chapter button and highlight it.