Help! excel inside word causes errors

I've got a delphi app that needs to update an excel sheet that's
embedded in a word doc.

No problem getting into the word doc & updating it, but when I try to
update some cells in the sheet, I get all kinds of intermittent

'Can't edit spreadsheet'
'Call rejected by callee'
'Server threw an exception'

Sometimes it works, sometimes it doesn't.  Here's the code:

ExcelObj :=

{about 20 variations on the following.  SomeThing is a currency
 ExcelObj.ActiveSheet.Cells.Item[Row,Co].Value :=

So, what's wrong here?  The 'Call rejected' error happens on one of
the cell assignments (the same one), sometimes.  

What's wrong with this picture?

Thanks a million for all suggestions.

Brady Wiseman