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

[Henry Drexler <alonup8tb@xxxxxxxxx>]

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.