help to find a string for 4th occurance

[Eddy Stan]

I need excel function at b7 to find a string of 7 chrs (at c7) for its 4th
occurance in E7 (text 300+ chrs) and pick next 17 alpha numeric digits (from
E7).

something like...at b7
=mid(e7, find(c7,E7,4th occurance), 17)

my advance thanks to you.

 

[Peo Sjoblom]

Try

=MID(E7,FIND("^^",SUBSTITUTE(E7,C7,"^^",4))+7,17)