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!

VBA isn't required for this. In B1, type in 100 as the first value. Then put this formula in B2 and fill down. This assumes that all duplicate values are contiguous, as in your example.

Formula:

=IF(A2=A1,B1,B1+100)