Vlookup-- case sensitive

I looked to see if someone had posted something about this but I cannot find it. I am using a vlookup command to do a simple match:

=VLOOKUP(A2,CHOOSE({1,2},F2:F10,E2:E10),2,0)

It works perfectly. However my data has exact same customer ID's and the only deferintation between the two is an upper or lower case symbol.

For example:


12345b
and
12345B

The function does not see a difference between these two numbers. Is there a way to incorporate a way to tell the vlookup function to "see" the upper and lowercase B as two different sumbols? I attached a sample of what the problem is. Thanks!