Finding Other Instances of Excel in a Macro

If you run a VBA program from within a particular instance of Excel, you can create other instances of Excel, open and modify workbooks in the newly created instances, and then close those instances. However, you may wonder how you can determine, within a macro, if other instances of Excel are already running, and, if so, take control of those instances.

There are a few ways you can go about doing this. If you simply want to know how many instances of Excel are running, you can use a macro that makes use of the Windows API. The following function implements this approach:

Public Declare Function GetDesktopWindow Lib "user32" () As Long
Public Declare Function FindWindowEx Lib "user32" Alias _
  "FindWindowExA" (ByVal hWnd1 As Long, ByVal
hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long

Function ExcelInstances() As Long
    Dim hWndDesk As Long
    Dim hWndXL As Long

    'Get a handle to the desktop
    hWndDesk = GetDesktopWindow

    Do
        'Get the next Excel window
        hWndXL = FindWindowEx(GetDesktopWindow, hWndXL, _
          "XLMAIN", vbNullString)

        'If we got one, increment the count
        If hWndXL > 0 Then
            ExcelInstances = ExcelInstances + 1
        End If

        'Loop until we've found them all
    Loop Until hWndXL = 0
End Function

This code was developed by Excel MVP Stephen Bullen. It obviously won't allow you access to the individual instances of Excel; it only returns a count of the number of instances open. If you want to develop code to use the instances, then you don't need to rely upon the Windows API. You can, instead, use code such as the following to determine if an instance of Excel is open:

Dim xlApp As Excel.Application
Set xlApp = GetObject(, "Excel.Application")

If an instance is running you can access it using the xlApp object. If an instance is not running you will get a run-time error. The GetObject function gets the first instance of Excel that had been loaded. To get to others, you can close that one and then try GetObject again to get the next one, etc.

If you want to set the xlApp to a particular instance of Excel, you can do so if you know the name of an open workbook in that instance:

Dim xlApp As Excel.Application
Set xlApp = GetObject("ExampleBook").Application

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (9451) applies to Microsoft Excel 97, 2000, 2002, and 2003.