Create Array BeforeReading

[Sam12485]

Hello,

I got a Question. I will create an Array WhileReading or BeforeReading (not sure what might be better atm).
This is how my Formula Looks like. Now i Want to put it in the Header with BeforeReading for Example.

        dim i as number 
         dim p() as number 
         
         for i = 1 to Count({AUFDRUP_TXT.POSNUM}) 
             if not ({AUFDRUP_TXT.HiMi-IDNr} = "00") and not ({AUFDRUP_TXT.REZANT} = 100) then 
                 redim preserve p(i) 
                 p(i) = {AUFDRUP_TXT.POSNUM} 
             end if 
         next i 
     
         Formula = minimum(p)

Header Part

beforereadingrecords 
 global pArr() as number 
 formula = pArr = 0

Detail Part

BeforeReadingRecords 
 Global pArr() as Number 
 Dim i as Number 

     for i = 1 to Count({AUFDRUP_TXT.POSNUM}) 
         If Not ({AUFDRUP_TXT.HiMi-IDNr} = "00") And Not ({AUFDRUP_TXT.REZANT} = 100) Then 
             Redim Preserve pArr(i) 
             formula = pArr(i) = {AUFDRUP_TXT.POSNUM} 
         end if 
     next i

But that doesn't work. Does somebody know where my issue is?
It says that the Count() can't be used and must be evaluted later.
Must I do the Count() in Beforehand?

Thanks for your help.