Creating non reoccuring random groups of people

So this isn't really an informatics question but I'm guessing the solution lies in informatics.

We have a group of 100 students that are meant to have discussion amongst each other. For this we want to separate them into 10 groups of 10 people. We want to have three rounds of discussions, however we want the groups to be different each time. No one person should get to sit with the same person twice.

Say we assign our groups letters abcdefghij (10) Person1 gets Round1:A Round2:B Round3:C Person2 gets Round1:A but then can't have Round2:B or Round3:C because they would then meet again.

Doing this by hand sounds pretty insane and I'm sure there is a pretty simple solution for this. Maybe even a program that does exactly this, but I just can't find it or don't know what to search for...

Sadly I have no skills whatsoever in programming, but maybe this can even be done in excel or sth like that?

All help or tips apreciated. Thanks for taking the time!