VBA for Unique Values

Hi there,
I need some help creating (what I think should be) an If statement.

I have a list of duplicate values, and need to apply a unique number to each occurrence of the duplicate value. I need this to be done automatically and advance by 100 each change in value. See below:

1/2/2015 - 100
1/2/2015 - 100
1/2/2015 - 100
1/3/2015 - 200
1/4/2015 - 300
1/4/2015 - 300

Thank you for any help!