Dumping chain created by fix bond/create

Hi all,
I’m using fix bond/create to create a molecule and I’m trying to dump just the molecule coordinates as it is formed. I’ve tried the following:

group chain type “list of types in molecule”
fix tmp all bond/create …
group dychain dynamic chain every 1000
dump mydump dychain custom 1000 dump.chain id type xu yu zu

But the number of molecules dumped is the same every time. Am I doing something wrong? Or is there another way to achieve what I’m looking for?