It's because the workbooks collection contains only open workbooks.

You can try the following, which checks all the open workbooks against the
path you've specified:

Sub test()

Dim path As String
path = "C:\blah.xls"

Dim wb As Workbook
For Each wb In Workbooks
   If wb.FullName = path Then Exit Sub
Next wb

Workbooks.Open Filename:=path

End Sub

You should be able to

I omitted to mention that i had added an "or" as follows:

If wb.FullName = path2 or path3 Then Exit Sub

which seems to cause the problem. using two if statments is not a solution
as obviously the exit sub of the first negates the second.

I could just write two subs but is there a better way?

Dim myPath as string
dim myFileName as string
dim wkbk as workbook

mypath = "C:\something\"
if right(mypath,1) <> "\" then
 mypath = mypath & "\"
end if

myfilename = "workbook.xls"  '<-- don't include the path here!

set wkbk = nothing
on error resume next
set wkbk = workbooks(myfilename)
on error goto 0

if wkbk is nothing then
 on error resume next
 set wkbk = workbooks.open(filename:=mypath & myfilename)
 on error goto 0
end if

if wkbk is nothing then
 msgbox "Not open and can't find it!"
else
 msgbox wkbk.fullname
end if

This assumes that C:\something\