I wouldn't, I would leave the message box.

I use error trapping for unanticipated errors, that situation that you have
is perfectly predictable. My code would look something like

On Error GoTo errHandler
'the real code

exitHandler:
'general tear-down code
Exit Sub/Function

errHandler:
MsgBox "Unanticipated error:" & vbNewLine & _
vbTab & "Err #: " & Err.Number & vbNewLine & _
vbTab & "Description :" & Err.Description
Resume exitHandler

HTH

Bob

"deltaquattro" wrote in message
...
Hi guys,

I'm not so used to the On Error statement, ssince I come from a
Fortran background where all error handling must be performed using If
Then Else constructs. Example: in this interpolation subroutine

'Returns an interpolated value of x
'doing a lookup of xarr-yarr
Public Function Interp1(xArr() As Double, yArr() As Double, X As
Double) As Double
Dim I As Long

If ((X < xArr(LBound(xArr))) Or (X xArr(UBound(xArr)))) Then
MsgBox "Interp1: x is out of bound"
Stop
Exit Function
End If

If xArr(LBound(xArr)) = X Then
Interp1 = yArr(LBound(yArr))
Exit Function
End If
'For i = LBound(xArr) To UBound(xArr)
' If xArr(i) = X Then
' Interp1 = yArr(i - 1) + (X - xArr(i - 1)) / (xArr(i) - xArr(i -
1)) * (yArr(i) - yArr(i - 1))
' Exit Function
' End If
'Next i
I = Locate(xArr, X) + 1
Interp1 = yArr(I - 1) + (X - xArr(I - 1)) / (xArr(I) - xArr(I - 1)) *
(yArr(I) - yArr(I - 1))
End Function


woudl you advise substituting the If...MsgBox combination with an On
Error statement? In general, how can I understand if it's better to
use On Error or to test for errors with If? Finally, a purely
programming style question: would you suggest to include the error
handling in the interpolation subroutine, or to move it in the caller
subroutine? Thanks,

Best Regards

deltaquattro