Sub Test()
Dim wb As Workbook
Dim srcWB As Workbook
Dim dstWB As Workbook
Dim wbCount As Long
' Capture current workbook (with macros)
Set srcWB = ActiveWorkbook
' Loop through all other workbooks
For Each wb In Application.Workbooks
' Count open workbooks (excluding Personal workbook)
MsgBox wb.Name
If wb.Name <> "PERSONAL.XLSB" Then
wbCount = wbCount + 1
If wb.Name <> srcWB.Name Then
Set dstWB = wb
End If
End If
Next wb
' Check to make sure only two workbooks open
If wbCount <> 2 Then
MsgBox "You do not have exactly two workbooks open"
Else
' Update cell A1 in first sheet of other workbook
dstWB.Activate
Sheets(1).Range("A1") = "This is a Test"
End If
End Sub