Self-Aware Macros

For some macros you may need to determine if there is a way to determine the particular machine on which the macro is operating. For instance, you may have a desktop PC that has a particular directory at D:\OraNT\Plus33, while your notebook PC has the directory at C:\OraNT\Plus33. The macro, of course, needs to detect which machine is in use so that it knows which directory to use for its processing.

There are different ways that this task can be approached. It is possible to create an Excel macro that actually accesses the Windows API and determines the name of the computer on which it is running. Such an approach can get quite involved, however.

An easier way is to just use VBA's DIR command to determine where the desired directory exists. The following will do the trick:

Sub OracleQueries()
    Dim sTemp As String
    Dim sGoodPath As String

    sGoodPath = "D:\OraNT\Plus33\"
    sTemp = Dir("D:\OraNT\Plus33\nul")
    If sTemp = "" Then
        sGoodPath = "C:\OraNT\Plus33\"
        sTemp = Dir("C:\OraNT\Plus33\nul")
    End If

    'Now have directory information
    If sTemp <> "" Then
        'Process queries using sGoodPath
    Else
        MsgBox "Directories not found!"
    End If
End Sub

Notice how the DIR function is used in this example. Normally DIR returns the name of the first file it finds in the requested directory. If the directory is empty, however, DIR returns an empty string—even if the directory actually exists. Since all we want to do is find out if the directory exists (not if there are files in it), it is necessary to append the letters "nul" at the end of the directory path used by DIR. This causes DIR to return an empty string if the directory is not located, or else the characters "nul" if it is (even if the directory is empty).

Toward the end of the macro, sTemp will be empty if neither directory could be located. If one of them was located, then sTemp will not be empty, and sGoodPath will be set to the directory name that can be used in further processing.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2607) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Self-Aware Macros.