Groovy rule to get user's group and prevent that group modify data row in a form

Hello everyone,

I have one question about groovy rule.

If a have 4 users : U1, U2, U3, U4 and (U1,U2) are in group A, (U3, U4) are in group B.

Now I have a form that both Group A and Group B can access.

But I want:

+ Group A can modify only the row has Member K = 1;

+ Group B can modify the other rows.

How can I write the Groovy rule to get the group and prevent a group from modifying data in specified rows?

Thanks!