Hi,
This is the step by step procedure
1. I am calling Excel Macro from VB.Net using Run command to open Excel
workbook. It works fine.
2. I made modification in that workbook.
3. I call Postmessage API to return the control back to VB.Net. In
VB.Net, I called again Run command to get the changed values from excel
workbook to vb.net parameters so that they can be saved into the
database. But everytime, I call Run command I get above exception.

Also Immediately calling Postmessage, I am giving user the option of
saving the workbook onto their hard disk drive. I don't know if the
problem is because of it.

Thanks
Nikki