Maximum Text String In A Column And Index Against It

I have trying to find the maximum date value in a series of campaigns with the same name [Combnined Campaign (Campaign)] , the aim is to pick the lowest version of the same name if the campaign is connected and pull the max end dates and number of weeks [Week Number Combined Campaign] that overall campaign has been running. A spreadsheet below explains this too.

What I need is to search for all the campaign names in column [Combined Campaign (Campaign)] and find the matching week number. What I am currently using is this formula:

=IFERROR(IF(E2="Yes",INDEX($A$1:$K$26,MAX(MATCH(F2,$G$1:$G$26,0),1),COLUMN($K$1:$K$26)),""),"")

Yet Max doesn't work with text.

Campaign Appeal Code
Launch Month
Market
Product
Combined Campaign (Yes/No)
Combined Campaign (Campaign)
Channel
Start Date
End Date
Week Number
Week Number If Combined Campaign

AAB13
Jan

Yes
AAB13
Mail
01/01/13
31/01/13
Complete

[Code] .........