I think it does allow what you're asking..
Log-in to your control panel, then go to Domains -> Manage Domains, then click the [DNS] link next to your domain.
From there you can type in a subdomain (wildcard subdomains are OK) and assign it a DNS record type (CNAME/NS/etc) and a value.
Or, if you just want it to redirect the browser to a webpage on your other host (easier, but you can't do anything fancy with it) you can click Domains -> Manage Domains, then click the "[Add New Domain / Sub-Domain]" link at the bottom. Then type in "yoursubdomain.yourdomain.com" in the Domain to redirect field, and put the URL of your other host's webpage in the Redirect to URL field and click "Redirect this domain now"
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