Boolean Operators as Variables

I've made a form that allows a user to select with radio buttons whether multiple search fields are treated as an AND or as an OR. They have the option to fill out some or all of the form fields. However, the problem I run into when I have null fields is that Splunk is unhappy with duplicate boolean operators (OR OR or AND AND). I can't simply use a default * because that will mess up OR.

My codes is as follows:

<form>
  <label>Search</label>
   <searchTemplate>index=Stuff ($Field1$ $andor$ $Field2$ $andor$ $Field3$)</searchTemplate>

  <fieldset>
    <input type="text" token="Field1"><label>Search 1</label>
     <prefix>DBField1="</prefix>
     <suffix>"</suffix>
     </input>
  </fieldset>

  <fieldset>
    <input type="text" token="Field2"><label>Search 2</label>
     <prefix>DBField2="</prefix>
     <suffix>"</suffix>
     </input>
  </fieldset>

  <fieldset>
     <input type="text" token="Field3"><label>Search 3</label>
     <prefix>DBField3="</prefix>
     <suffix>"</suffix>
     </input>

     <input type="time">
     <default>Last 30 days</default>
     </input>

     <input type="radio" token="andor">
     <label>AND or OR</label>
     <choice value="AND">AND</choice>
     <choice value="OR">OR</choice>
     <default>OR</default>
    </input>
  </fieldset>

</form>

Is there anything that can be done? I've tried numerous rows of eval if(Field1="Field1=&qu ot;&qu ot;"), but all I end up is Splunk Handler exceptions.