The error says " Run-time error '9': Subscript out of range". The excel workbook doesn't have any details in it when created. I debugged the code to see where it is failing. Its failing here
For i = 1 To .Comments.Count
With .Comments(i)
StrCmt = StrCmt & vbCr & .Reference.Information(wdActiveEndAdjustedPageNumber) & vbTab & .Range.ListFormat.ListString & vbTab & .Author & vbTab & .Date & vbTab & .Scope
StrCmt = StrCmt & vbTab & Trim(Split(.Range.Text, ":")(0)) & vbTab & Trim(Split(.Range.Text, ":")(1))
End With
Next