The extra explanation clarifies things a bit, but the posted formulas
still work for me, if I understand the problem correctly. Could there
be typos?

Below is a slightly simplified version starting from a fresh sheet.

In the fresh sheet put this in A2:
=IF(ISERROR(FIND("relief",MasterTab!O21)),"",MAX(A $1:A1)+1)
and this in B2:
=IF(ROW()-1MAX(A:A),"",
OFFSET(MasterTab!$BB$21,MATCH(ROW()-1,A:A,0)-2,0))
then select A2:B2 and copy down to row 73.

Column B should contain the desired list. Column A is a helper column,
and can be hidden.

With your latest data, I get 1 in A17 and 2 in A39, corresponding to
the rows in MasterTab!O21:O92 containing the word "relief" somewhere
in the text. The rest of column A is blank. Then, B2 reports what's in
MasterTab!BB36 and B3 reports what's in MasterTab!BB58. The rest of
column B is blank.

If it's still not working, there's a way to see step-by-step how Excel
is evaluating a formula. Select the cell containing a formula and use:
Tools Formula Auditing Evaluate formula
This might give a clue how to correct a formula.

(I have Excel 2003.)