assistance with max consecutive occurrences in a manipulable range, please

[Bab1]

Kind People,
I need assistance with a complex formula (for me at least) to count the max consecutive occurrences a a letter in a range. The range in which to search however' should be manipulable - if possible.
I attached a sample of the basic spreadsheet I am working on - where I point out where my problems lie.
Your kind assistance will be appreciated - as always.
Thank you kindly and regards.
Bab