I am importing an Excel file with existing data using the Import wizard to build my table. It has an ID field (CID) which I would like to keep and set to auto increment starting with the next number.
Can this be done ?

Yes. Create the table first and set the CID to autonumber. Append your existing data and Access will start numbering from your highest value.

Be aware, however, that autonumbers are not guaranteed to be sequential and contiguous. If that really matters you need to do your own. Search in here for 'sequential number' and 'DMax'

Thanks
I appreciate the info.