If you want to extract all but the last two characters, you can do this by using two text functions. The following function will work on any length text string. It is extracting the text from cell A1.
=LEFT(A1,LEN(A1)-2)
The LEFT function extracts a number of characters from the left of a string of characters. Because the number of characters could be variable, we use the LEN function to tell us how many characters in cell A1, and then simply deduct 2 to tell the LEFT function how many characters from the left to extract. The 2 could be replaced by a cell reference to all allow you vary the number of characters to omit.
Note: an amendment to the above formula will cater for cells with one or two characters.
=LEFT(A1,MAX(0,LEN(A1)-2))