I have created an Excel (2003) using a VB Form for data input (and
validation), which, after the user finishes with entering information,
returns values to the sheet behind it, in order to carry on with calculations.

The problem now is that users started calling this Excel from IE: a web page
links to the Excel, they click the link and the Excel file opens inside IE,
as an embedded object to the web page.
When opened like that, the form I am using inside the Excel loses access to
the worksheet object model behind it:
the reference to the "Activesheet" now returns an error 91 (object variable
or with block.....)

How can I regain access to the Worksheet object model from the form, when
Excel is opened inside IE?