How to use constant values in Excel UDF?

Question

I've been struggling to come up with a UDF in Excel. basically what I'm looking for is a function that would take 2 input parameters(constant) provided by a user, then the function would return one of the values pre-stored in an excel table somewhere. Here's what it would look like:

month Peak off

1. January 320 176
2. February 320 128
3. March 368 252
4. April 352 128
5. May 305 320

The function would be like this: =Hours(February, Peak) then it would return February peak hours and so on.

I appreciate all the help. Thanks a lot

EDIT: Code added as comment

Public Function calculateHours(ByVal mo As Variant, ByVal period As Variant) As Integer    
 Dim tablette As Range 
 Set tablette = Worksheets("Hours").Range("U4:V15") 
 Set valueRange = Worksheets("Hours").Range("U4:U15") 
 period = "peak" 
 For Each ref In valueRange 
   mo = WorksheetFunction.VLookup(ref, tablette, 1, 0) 
 Next 
 ref calculateHours = WorksheetFunction.VLookup(mo, tablette, 2, False) 
End Function

When I try to use this function such in =calculateHours(january, peak) I only get the last value from table regardless what the parameters are

Answer 1

Consider:

Public Function ReturnVale(period As String, MinMax As String) As Variant
    months = Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")
    Off = Array(330, 347, 366, 393, 307, 353, 310, 347, 332, 307, 400, 333)
    Peak = Array(399, 428, 440, 446, 366, 431, 370, 413, 389, 364, 470, 421)
    For i = LBound(months) To UBound(months)
        If period = months(i) Then
            GoTo done
        End If
    Next i
    ReturnVale = "NOT FOUND"
    Exit Function
done:
    If MinMax = "Peak" Then
        ReturnVale = Peak(i)
    Else
        ReturnVale = Off(i)
    End If
End Function

Naturally you would modify the Array() statements to match your requirements.