Adding bottom borders to list of names, Conditional Formatting?

We use huge spreadsheets in my job and at this point I have about 250 names each day that I need to put into a spreadsheet and add a bottom border line to the last row in each name group, to separate the names for ease of reading/data input.  Some names have 2-6 lines of data and I need the name to be on every line.  Is there a way to highlight a group of cells and add the bottom border to an entire ROW of data based on the last name in a specific cell?  For example, if Smith has 4 rows of data, followed by Jones with 7 rows, and Patel with 5 rows, how do I select all 16 rows and give a command/formula that will return a bottom border line to ONLY the last row of Smith, last row of Jones, and last row of Patel?  The spreadsheet already contains a ton of formulas/data/conditions so I'm afraid to convolute things further, but adding individual lines is taking too long! I understand I can CTRL select all those rows I want to underline, but that is my current process, and it simply takes too long!  I'm hoping there is a formula/conditional format option to help!