Loop da loop.

So... I never thoght I'd ask this around here, specially asking for Matt =p but I think I REALLY NEED to loop - and that boring popup won't let me.

I have an excel, extracted from a website, where i have account numbers, descriptions and values. Problem is: no all "account numbers" field have the account numbers, some have details from the "previous" account. But there isn't only one such detail, and the ammount of details is variable.

One transformation I thought could help me here would be to:
Input -> lag -1 for account number -> set account number as detail_type -> Filter for regex, account numbers starts with 3 digits.

Filter positive, goes on with sort and output. Filter negative, would be the start for the loop.

Filter -> Select values to set account number as the lagged account number -> lag -1 for new account number -> Filter.

hm... I just realized I'd have to filter some of the original excel's "header" rows before that loop, or else I'd really do have some rows that would be circling forever inside it.

But anyway, I really do need to automatize this since each xls has some 900 accounts, with some 2000 details, and there are some 300 xls files.

Any tips? =p