Nostalrius Begins - Quality wow vanilla realm (1.12)

No addon section as far as i can see.I've seen some similar threads on the internet,but they concern later expansions , not vanilla,so probably it won't work.

I find shift/alt/ctrl a bit uncomfortable to use as modifiers.I stretch my fingers too much and it's just...bad.
Is there any way i can instead use my mouse buttons as modifiers in macros specifically?

For example i want a macro that will cast my frostbolt and when i press modifier it will cast rank 1 frostbolt instead.

Something like this:

/run local x = IsShiftKeyDown(); if x == nil then CastSpellByName("Frostbolt") else CastSpellByName("Frostbolt(Rank 1)"); end;

Instead of shift modifier i want to use my mouse buttons like this(yeah i know it doesn't work i tried it)

/run local x = IsMouseButton4Down(); if x == nil then CastSpellByName("Frostbolt") else CastSpellByName("Frostbolt(Rank 1)"); end;

Thanks

change mouse buttons in mouse software to shift