make multiple text boxes required if check box ticked

I am using this script

this.getField("cust Tel No").required = !event.target.isBoxChecked(0);

and it works but when i try and add extra text boxes it doesnt, where am i going wrong

this.getField("cust Tel No").required = !event.target.isBoxChecked(0); &&

this.getField("cust Tel Ar").required = !event.target.isBoxChecked(0);