@steveturley 

After BR on SCTask table 

Conditions

State changes from pending

and request_item.state is not WIP

On insert and update

in advance Script

var task = new GlideRecord('sc_task');

task.addQuery('request_item',current.request_item);

task.addQuery('state','-5');// replace back end value mostly it will be numeric value

task.query();

if(task.next()){

//do nothing

}else{

var gr = new GlideRecord('sc_req_item');

gr.get(current.request_item);

gr.state = 'WIP';// replace back end value mostly it will be numeric value

gr.update();

}

My bad that should be not != just pending try above code