how to use TTable.IndexFieldNames Property

  I'm accustomed to using the TTable.IndexName property, however i am in a
situation in which i need to create different indexing combinations at
runtime.  my
understanding of the TTable.IndexFieldNames property is that you can use
this
property to specify one or more fields (seperated by semicolon) to index by,
providing they are indexed fields.  in my case i am doing just that. it
works fine if i just specify one field, but if i specify more than one field
i get an error stating that my
table does not have an index for these fields even though i do.  in fact not
only do i have an index for each field, i even have an index for the
different combinations that i've tried.  is this a bug or am i missing
something???????!!!!!!!!!!!!!!