How do pre and post macro spells get used

Lazy Macros How To's
1

I was wondering how pre and post macro spells get used. For example, if you had:

Sequences['DPS'] = {
PreMacro = [[
/targetenemy [noharm][dead]
/cast Pre1
/cast Pre2
]],
	'/cast SpellA',
	'/cast SpellB',
	'/cast SpellC',
PostMacro = [[
/startattack
/cast Post1
/cast Post2
]],
}

If you clicked the button this was bound to 3 times, would the clicks be:

Click 1 - Pre1,Pre2,SpellA,Post1,Post2
Click 2 - Pre1,Pre2,SpellB,Post1,Post2
Click 3 - Pre1,Pre2,SpellC,Post1,Post2

If so, then anything in the pre or post that is on the GCD would mess things up, yes?