[TYPO3-english] Typoscript: override for multiple checkboxes if these are checked

[Bert Hiddink [BENDOO e-work solutions]]

Hello,

I am with TYPO3 6.2 and tx_news. I have the following snippet:

...
         renderObj=TEXT
         renderObj {
            field=title
            wrap = <div class="filter"><input 
name="tx_news_pi1[overwriteDemand][categories]" value="{field:uid}" 
id="chb{field:uid}" class="chbFilters" type="checkbox">&nbsp;|</div>
            wrap {
               insertData=1
               override = <div class="filter"><input 
name="tx_news_pi1[overwriteDemand][categories]" value="{field:uid}" 
id="chb{field:uid}" class="chbFilters" type="checkbox" 
checked>&nbsp;<i>|</i></div>
               override {
                   if {
                     isInList.field = uid
                     value.data = GP:tx_news_pi1|overwriteDemand|categories
                   }
               }
            }
         }
...

This works, that is, but only for the last checkbox checked from 
GP:tx_news_pi1[overwriteDemand][categories]

So I thought adding an uid to each var like this:
...
         renderObj=TEXT
         renderObj {
            field=title
            wrap = <div class="filter"><input 
name="tx_news_pi1[overwriteDemand][categories][{field:uid}]" 
value="{field:uid}" id="chb{field:uid}" class="chbFilters" 
type="checkbox">&nbsp;|</div>
            wrap {
               insertData=1
               override = <div class="filter"><input 
name="tx_news_pi1[overwriteDemand][categories][{field:uid}]" 
value="{field:uid}" id="chb{field:uid}" class="chbFilters" 
type="checkbox" checked>&nbsp;<i>|</i></div>
               override {
                   if {
                     isInList.field = uid
                     value.data = 
GP:tx_news_pi1|overwriteDemand|categories|field:uid
#                    value=3051,3057
                   }
               }
            }
         }

However, GP:tx_news_pi1|overwriteDemand|categories|field:uid does not 
work. How could I check for each variable in the override if I want to use:
tx_news_pi1[overwriteDemand][categories][{field:uid}]

???

Any ideas? Thanks in advance!

Regards,
Bert