Analytic type functionality, matching patters in a column then increment an integer

I can do this in excel with vba, though due to the volume of data that is
now impracticable and I am trying to move most of my logic into the query
and db for analysis.

Looking at the analytic functions I see no way to carry values over the way
they need to be.

Example column:

I have a column that evaluates to either tf,tt,ft,ff (true false matches).
tf means the start of a section,
tt mans intermediary but in the good section
ft means the end of the section that needs to be marked.
ff is just ignored

so I can have
'evaluation'
tf
tt
ft
ff
ff
tf
ft

and would like to have a column indicate like this:

'evaluation' 'indicator'
tf 1
tt 1
ft 1
ff
ff
tf 2
ft 2
tf 3
tt 3
ft 3
ff

I have tried rank() and some case statements though I can quite seem to get
the sql to be aware across rows as shown in the desired indicator column
noted above.

It seems like I am missing something that would we aware like that. Any
ideas? Thanks in advance.