Finding the highest value in a column and changing the group

[abuchan]

Attached is a sample file which is part of a bigger project which is slowly coming together. Sheet1 includes three columns (A) 'parcelnumber', (B) 'improv_id', and (C) 'bld_num'. I need to create a fourth column which shows how many (total) buildings are associated with a specific parcel number. On Sheet 2, I have hand-created what I am trying to obtain. In essence, I am hoping to show that an improvement is 3 of 4 or 1 of 1 or 7 of 15 and so on. The 'real' file has approximately 40,000 entries so it is a little more than is realistic. Also, as this is part of a bigger project, I am hoping to complete this task as a macro.

Thank you for any insight you can provide.