find the middle number in array

Of course, cappymer1 is right about the home work, but it's my birthday today. So you are in luck. The following function is a UDF. Place it in a standard code module (not ThisWorkbook, and not one of the Sheet modules). Call it from the worksheet by entering something like this in a cell of your choice:

 =MiddleNumber(B1:B9)

Function MiddleNumber(Rng As Range) As Double

    Dim Arr As Variant
    Dim n As Long
    Dim i As Long
    
    Arr = Rng.Value
    On Error Resume Next
    n = UBound(Arr)
    If Err Then
        MiddleNumber = Arr
    Else
        i = Int(n / 2) + (n Mod 2)
        If (n Mod 2) Then
            MiddleNumber = Arr(i, 1)
        Else
            MiddleNumber = WorksheetFunction.Min(Arr(i, 1), Arr(i + 1, 1))
        End If
    End If
End Function