title: Dojo combobox check values
body: <p>I'm currently working with Dojo and i'm fairly new to it.
  I'm running into a problem where I want to check the contents of a combobox if the userinput is valid or not.
  If the input is invalid I want to prevent a POST action from happening after submit is being pressed.
  Invalid input would be characters like {}&lt;>;' etc. I only want to allow text and numbers with a regexp, the input must be more than 0 and less than 20, so the field may also not be blank.</p>
  
  <p>The user MUST be able to enter his/her own custom text and not only choose from the already available items, if that was the case I should've used a FilteringSelect.</p>
  
  <p>Thanks in advance</p>