document.calcForm.user_nameDol.options[0]=new Option("Брянск");
<select name="user_nameDol"> <option></option> </select>
document.calcForm.Oblast.options[0]=new Option("Брянск"); document.calcForm.Oblast.options[0].value = 1;
document.calcForm.Oblast.options[0]=new Option("Брянск", 2);