I think easiest options might be to build your UI with H List Boxes instead of V List Box or by using Table Box / Lineup box.
With H List Box you can use Align("center"), with Table Box they should be aligned and same with Lineup Box. With Lineup Box you might want to use Lineup Ruler Box to modify the widths of each column
Names Default To Here(1);
strGroupColName = "Group";
lstGroupId = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"};
nw = New Window("",
Lineup Ruler Box(
Widths({50, 25,30,25,30,25,30,25,30,25,30,25,30}),
lub = Lineup Box(N Col(11),
Text Box("Group"),
Text Box("Grp"),
Text Box("Ctrl"),
Text Box("Grp"),
Text Box("Ctrl"),
Text Box("Grp"),
Text Box("Ctrl"),
Text Box("Grp"),
Text Box("Ctrl"),
Text Box("Grp"),
Text Box("Ctrl")
);
);
);
For Each({groupid}, lstGroupId,
lub << Append(Text Box(groupid));
For(i = 1, i <= 10, i++,
lub << Append(Check Box(""))
);
);
-Jarmo