Question

Why is it when I use Err.Raise 65536 the Err.Number will actually have the value of 5 and not 65536?

According to Raise definition: Sub Raise(Number As Long, [Source], [Description], [HelpFile], [HelpContext]). The passing parameter is Long and Err.Number is also Long.

So why can’t I use values greater then 65535?

Private Sub Command1_Click()
Dim a As Long
    On Error GoTo ErrCatch
    For a = 0 To 99999
        Err.Raise a
        DoEvents
    Next a
    Exit Sub
ErrCatch:
    ' this is where Err.Number is evaluated
    Resume Next
End Sub`

Answer 1

From the MSDN documentation:

Number

Required. Long integer that identifies the nature of the error. Visual Basic errors are in the range 0–65535; the range 0–512 is reserved for system errors; the range 513–65535 is available for user-defined errors. When setting the Number property to your own error code in a class module, you add your error code number to the vbObjectError constant. For example, to generate the error number 513, assign vbObjectError + 513 to the Number property.

So even though you can submit a value larger than 65535, anything larger than 65535 will become Error 5.