Loop through strings stop when strings change and start looping in the next column...?

Hi, I am looking to find the syntax to make a loop that does this:

I have 3 columns.

The first column holds repeating strings, after an irregular number of rows the string changes e.g. aa, aa, aa,... bb, bb,bb,bb,bb,... cc,cc,cc

I would like to know how I can tell the for loop to loop through aa, than loop through column 2 and 3 (to find the items I am looking for) and then continue looping through column 1 with bb.

I added arrows in the excel file to indicate the route the loop should take.

Any suggestions would be much welcome.