XML schema validation of one xml block based on values from another xml block

[Andy]

Hi!

Is possible to do xml validation of one xml block based on values from
another xml block?

For example, I have an input xml file containing account types.
<Root>
<AccountTypes>
<AccountType></AccountType>
…………………………………..
</AccountTypes>

<Accounts>
<Account>
<AccountType></AccountType>
</Account>
</Accounts>
</Root>

Is there a way I can put restriction in schema that <Account> must
have only such <AccountType> that are listed in <AccountTypes>


The file size is 20-25 MB. (It would not be a good idea to load it
into DOM)
It is preferably to catch it before processing will start

Thank you,
Andy