This is not an html plugin, it is a VB/VBA function that has no preview, to see it working, you need to add it to your VBA project

If you don't have an idea of what is it, then this is not for you

Option Explicit

Sub Sample()
Dim Ret
Ret = IsWorkBookOpen("C:\myWork.xlsx")
If Ret = True Then
MsgBox "File is open"
MsgBox "File is Closed"
End If
End Sub

Function IsWorkBookOpen(FileName As String)
Dim ff As Long, ErrNo As Long
On Error Resume Next
ff = FreeFile()
Open FileName For Input Lock Read As #ff
Close ff
ErrNo = Err
On Error GoTo 0

Select Case ErrNo
Case 0: IsWorkBookOpen = False
Case 70: IsWorkBookOpen = True
Case Else: Error ErrNo
End Select
End Function