Look-up And Insert Row

In column B, there is a list of companies. In column C there is the sales value for each company with sub totals after each type of company. For eg:

B3 - Header 1
B4 - Company name
B5 - Company name
B6 - Sub Total

B8 - Header 2
B9 - Company name
B10 - Company name
B11 - Sub Total

What I need to do is create a macro to look down column B for the cell containing "Sub Total" and insert a new row above. I will create a button to do this. So, if I want to add a new company under header 1 I will press button 1 and a row will be inserted above the header 1 sub total. The same will apply if I want to add a new company under header 2 and so on.