Lookup in matrix

[julianF]

Hi all,
I would like to make a lookup in a matrix.
In the attached example, I want to get in the column B of Sheet1 the value of the column A of Sheet2 which row contains the correspondent value of column A in Sheet1.
In other words, what I represented in column C of sheet1.

I tried with VLOOKUP in column B of Sheet1, but unfortunately it works only when the found value in sheet2 is in column A; on the contrary, I need to get it even when it is in column B and C.

Please help!

Thank you and regards.
Julian.