[dba-VB] Query question

Working in the query designer in ASP.Net, I want to build a datatable
of rows which do not have a date in a particular field.  In Access
this is easy:

Select * From myTable where not IsDate(DateShipped)

But the ASP.Net query designer says that IsDate is not a valid function.

I can actually work around this by testing for null, but I'm still
curious about the IsDate function.  Visual Studio help shows IsDate as
a valid T-SQL function.

Thanks,

Doug