Your LDAP string is wrong - use:
LDAP://celtestdomdc1.celtestdom.local/CN=Users,DC=celtestdom,DC=local
or even this (server-less binding - goes to the default DC)
LDAP://CN=Users,DC=celtestdom,DC=local
First, the parts need to be separated by comma (,) not semicolon - and second, you need to use the DC=.... for all DNS-parts of your domain.
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Also you might want to look at my ADSI browser called Beavertail which is written in C# and 100% free and open-source. It will show you what your domain tree looks like and what the valid LDAP paths are.
</shameless plug>