Homebrew item question - adding spells to items

Hey everyone, I have this homebrew item that can cast both Guiding bolt and Cure wounds, but it uses Charisma as its spell modifier. However, right now it will pick the character's regular spell modifier. Is there a way to replace that? Cause I can add Charisma, but that doesn't do anything if the character already has another spell modifier.

Thank you for your reply! I already had an inkling it wouldn't be possible but I thought maybe someone knew something I didn't.

Unfortunately it's not my idea but my DM's. He doesn't work with D&D Beyond, but I do so I'm creating the homebrew item myself. I'm playing a Profane Soul Bloodhunter, which basically is a Warlock light. This ring is from my patron and I think that's why he chose Charisma, even though a Bloodhunter uses either Wisdom or Intelligence as their spellcasting modifier. I wouldn't have done it that way either, but ultimately it's his decision. I wouldn't have done it that way either, I would've just let it be the person's own spellcasting modifier.

But you have given me an idea to just modify the spells to my charisma to reflect the right numbers, so thanks again!

From what I’ve tested, there still doesn’t seem to be a clean way to force a magic item to use a different spellcasting ability than the character’s own stat.

If the item is set up to cast existing spells, the system usually defaults to whatever spellcasting modifier the character already has. The most reliable workaround I’ve found is to treat it like a fixed-power item and manually set the spell attack bonus / save DC to match the intended Charisma value.

It’s not as elegant as a true CHA override, but in practice it gives the right numbers on the sheet and avoids weird class interactions.