[TYPO3-dev] restrict flexform field for backend user in own extension

[Dominic Garms]

Hello,

I have a bug in an extension of mine and I dont know how to solve it: in 
flexform I have a textarea field where I want to provide restriction for 
user rights:
    <extends>
        <TCEforms>
             <exclude>1</exclude>
 
<label>LLL:EXT:dmf_galleria/locallang_db.xml:tt_content.pi_flexform.extends</label>
             <config>
             <type>text</type>
             <wrap>OFF</wrap>
             <cols>48</cols>
             <rows>8</rows>
             </config>
          </TCEforms>
       </extends>

What else do I have to do inside of the plugin for getting the 
restriction running, what kind of code has to get into flexform / php? 
Can somebody send me a link for a HowTo?

Thanks a lot

Best Regards,

Dominic