如何标记下拉列表，因此第一项不是标签，可能还有一个输入字段

I would like this dropdown box to have a label "select so and so..." and when the user pressed the carret, the dropdown list is displayed and the first item on that list be a blank selection not the label name. How would i accomplish this? Is there a way to put a input box inside? The dropdown is basically a operator selector, " =, <,>" and a dollar amount. Such that when I do this it will search SQL for the a requisition for a dollar amount equal to, less than, or greater than the amount selected.I would like this dropdown box to have a label