Can I Use Macros to Override Damage Types?

So I'm currently trying to set up a gunslinger in 5e using this homebrew  and am new to using macros. Just so anyone reading this doesn't need to scroll through the entire class, the gunslinger has an ability to create different forms of bullets, one of which (Incendiary bullets) replaces the usual Piercing damage with Fire, but it adds no additional damage. I currently have the Incendiary Bullets listed as a Global Damage Modifier. My thought process was that I could replace the damage type of my characters revolver with a macro that checks to see if the Incendiary bullets are being used and change the damage type accordingly. I'm just not sure how to properly write this out. If anyone can help me out it would be greatly appreciated!

if you are using the attacks from the sheet, then I dont think so, you'd need an API to modify your sheet entries 'on the fly'.  If you write your own macros for your attacks, then yes, you can include a query to ask what damage type it should be, although I'd hate that myself if 90 pct of the time I was using normal bullets, and would write a separate macro for special bullets.  You may be able to simply define a second 'phantom' weapon that has the stats for the alternate ammo loadouts as an entry in the sheet though.