How to assign task to particular Identity, when other activities is also there?

Hi Experts, I have a workflow like this, Prepare Drawing-----------yes--------------->Approval from HOD--------------yes------------>Upload Doc On "Prepare Drawing" activity has 3 Identity: Designer(dept 1) , Designer (dept 2) , Designer (dept 3) who has voting weight as 33, 33, 34 respectively, so after voting total is 100% it will go for "Approval from HOD" for approval.   Activity "Approval from HOD" has assignment for 3 Identities: HOD(dept 1), HOD(dept 2), HOD(dept 3). If HOD(dept 1) and HOD(dept 2) vote "yes" workflow gets promote, and HOD(dept 3) votes NO, It will again come back to Previous activity  i.e "Prepare Drawing", this all work fine, but when HOD(dept 3) votes "NO", How can I Send assign a task to "Designer(dept 3)" only, because on "Preparation of Design" Activity there is assignment to 3 identities i.e. Designer(dept 1) , Designer (dept 2) , Designer (dept 3) . and task is assign to other two Identities also and that is obvious thing. So, Is it possible to assign task to particular Identity i.e to Designer(dept 3) on Vote "NO"?   Regards, Maddy.