Last cell with text

[chameleon_crp]

Is there a formula that will tell me what was the last text in a range that has blank cells? All the cells have formulas and the blank cells have formulas with the outcome of "".
Example:

COLUMN A COLUMN B
ROW 1 A
ROW 2 X
ROW 3 X
ROW 4
ROW 5
ROW 6 A

The formula i am looking for would look up the range A1:B6 and look up the last text before the A in column B which should be an X.

 

[chameleon_crp]

This is what the columns and rows suppose to look like:

Column a
row 1 blank("")
row 2 x
row 3 x
row 4 blank("")
row 5 blank ("")
row 6 blank ("")

column b
row 1 a
row 2 blank ("")
row 3 blank ("")
row 4 blank ("")
row 5 blank ("")
row 6 a