Finding and filling values from another column, probably using OFFSET

Hi,

I'm trying to achieve something using probably offsets but i'm not quite sure how that would work. This is my simplified table:
excel21qx3.png
As you can see, theres multiple groups and not all the loanIDs are filled up. The helper column C should basically show the LoanID for the group.

So basically, I need a formula in column C that will populate the LoanID for each group its in. This should be the final result:
5-27-201611-18-29am0suvh.png

Any ideas?

Thanks,
Rob

Thanks!!!! That did it!!!