Trying determine the number of unique occurances

Hi To All-

I am having trouble trying to develop a formula that will count the unique months for a given ID.

Two sheets, the first has the Unique ID and that is where I want the formula.

The second sheet has one to multiple entries for each unique ID on sheet 1

I have attached a worksheet showing what I am trying to do. I've played around with this all morning, search the Web but haven't found the answer.

Any help you can give me will be extremely appreciated.

Thanks,
Jim