VBA code to insert a blank row after Subtotal row in excel 2003

Here is part of my excel data: (the actual excel file has hundreds of rows )

CityID      Quantity            
1                  3
1                  4
1                  4
Subtotal:  11
2                  3
2                  5
Subtotal:   8
Total:         19


I want to insert a blank row after each Subtotal row, format subtotal row in bold and size 11,  total number is single underlined.
Last row Total row is bold , size 12, and number is double underlined.
the result is as below.

How do I write VBA code to do it? thanks,
Result.jpg