Macro to create/update an Outlook contacts group

Hi,

I've got an excel sheet with a list of email addresses. This sheet is a shared list, which means other users can also perform updates.
I need an macro to create/update a contact group in Outlook using this list.
however, there are certain additional validations need to be performed while running this macro.
1. Duplicate entries needs to be removed
2. Email addresses needs to be validated against Outlook Global Address List and if there are entries that cannot be found in GAL it should be prompted whether to add those email addresses to Contact group or not.
3. Once the Contact group is created, macro should only update the same group without creating new duplicate groups
4. If there are multiple email addresses within one cell in the excel sheet, separated by "," or ";" those must be considered as separate email addresses.

Highly appreciate if anyone can help me on this!

Hi, if anyone can at least support me on achieving point No.2 validation, that'd be really helpful.. Thanks