[Zope-DB] How to overcome "Missing input variable"

[s_ronit]

Hi

I am trying to create a form that will select field id
when Field name was chosen.
The user choose Station name (in the form) and I want to
pass the Station Id on to the 
FormProcessor, and not the StationName.

The user doesn't know the Station id, just StationName.
How do I send to AddData.sql the StationId ?
I keep getting the Error :

   Missing input variable, StationId 

Here is the form Example1.dm (DTML-Method):

<dtml-var standard_html_header>

<dtml-if submit>

  <dtml-call AddData.sql>
  <a href="Example1.dm">Back</a></li>

<dtml-else submit>

  <form action="Example1.dm" method="POST">
    <select name=StationName style="width: 100" return
true;>
      <option VALUE="">
      <dtml-in SelectStationName.sql>
        <option VALUE="<dtml-var StationName null="">">
        <dtml-var StationName null="">
        <dtml-var StationId null="" >
      </dtml-in>
    </select>
    <input type="Submit" name="submit" value="Add">
  </form>

</dtml-if>

<dtml-var standard_html_footer>

And SelectStationName.sql: (Z SQL Method)

 select StationName,StationId from Stations

And AddData.sql: (Z SQL Method) input variable=StationId

 Select * from Stations 
  <dtml-sqlgroup where>
    <dtml-sqltest StationId op=eq type=string>
  </dtml-sqlgroup where>


Thanks
Ronit