change the status of remaining vendors when 1 vendor is approved

Hi all ,

Hope u r reading this with a good health.

I am having 4 lines for four vendors , for each vendor I click on enter reply and form opens with a workflow enabled on it.

In this way I will submit all the four vendors. when my approval approves any one of the vendors , the remaining vendors should get rejected.

I am not sure exactly where to write the code for it .

ny1 plz guide me for this.