I want to find the instance of a value and insert a row before and one
after the last instance of the same value.

Data is in column A:G, but the value to find is always in column A.

The first value is "GroupA"
The second value is "GroupB"

Before the first instance of "GroupA", insert row and label "GroupA
Start"
After the last instance of "GroupA", insert row and label "GroupA
End".

Then the same for "GroupB".