Basically you have your default bar.
You have your default glyphs.
You have your original talents.

When you purchase a dual spec:
You have the talents reset.
You have no glyphs for the second spec.
Your bar should be the same as the original as far as which spells are where.

As you change which spells appear in which places, wow remember separately for each spec.
If you were to make a macro like the above, you'd have to drag it onto the bar for each spec.
Thereafter wow should remember the macro is on each bar.
The only real advantage to this is there are a finite number of macro's available.
If you're not running out of macro's you can just have a macro for each spell, one per spec.