Open Excel Spreadsheet in Frame

I have a web based domino document management system where attachements are emailed into a database. The user opens a a frameset with a view of all attachments in the left frame. When they click on an attachemnt it opens in the right frame. This works fine for tiffs, jpgs, docs, pretty much anything EXCEPT excel spreadsheets which open in a new excel spreadsheet. Does anyone know how to get it to open in the right hand frame?My code in the left hand view for the a href is:

“<td class=viewCell width="40%">” +

“<a href='/” +@Subset(@DbName;-1) + “/0/” + @Text(@DocumentUniqueID) + “/$FILE/” +

@AttachmentNames + “’ target=‘framePreview’>” +

@Right(@AttachmentNames;@Length(@AttachmentNames) - 36) + “” +

“”

Please, this is killing me.

Apologies if the answer is on this formum, but I couldn’t see it if it is.