Middle number function

I have an assignment for my engineering class in which I must write a VBA program that finds the middle number of three numbers. My program compiles, but it returns 0 each time. I am not sure what I am doing wrong. Here is the code:

Option Explicit
Function FINDMID(a, b, c)
Dim x As Single, y As Single
If a > b Then
a = x
Else
b = x
End If

If x < c Then
x = y
Else
c = y
End If
FINDMID = y

End Function