How can we have a UDA defaulted from another UDA which already had values

Dear All,

  We have a multirow attribute group defined. It has multiple attributes whose values can be defaulted from another single row attribute group. I do not see any way by which we can achieve this defaulting. Everytime user clicks on Add Another Row of multirow AG, one has to fill in all the values manually. For ease business wants a way by which we can have the values defaulted from another single row attribute group. And then the user can change whichever of them required.

Do any one of you has any suggestions as to how this can be achieved?