The execute  method initiates an action. A workbook is not an action and
cannot be executed. Did you mean to use Activate? If not, could you give us
more information on what you are trying to do?

I am extrememly sorry..I meant workbooks("name")activate. I have checked for the
vba references but to no avail. The excel version is also same 2003. That's a
very basic statement  then why should it give error  on some machines while on
others it works  fine?

Some things you could check:

Was the specified workbook open on the machines where the command failed?
Was the name of the workbook spelt correctly?
Were some of the machines set to show file extensions so they would need the
.xls on the workbook name?

If none of these helps, what error  message was produced?

I was able to reslove the issue.Actually i didnt put the extension.xls.Hence
some machines gave error
I have modified the stement from workbooks("IATOOL").activate to
workbooks(IATOOL.xls")

I would try the following statement.

Workbooks("IATOOL.xls").activate