Uttam notes that when he looks at the Page Setup dialog box he can specify a paper size for his worksheet. He wonders if there is a way that he can specify a custom paper size, different from those listed in the Page Size drop-down list.
Unlike Word, which can accept custom page sizes and can bypass the printer driver to force the printer to accept it, Excel gets its list of page sizes from those defined in the printer driver. This is why there is no way to set a custom page size in Excel.
That being said, some printer drivers do allow you to define custom page sizes. Understand, however, that this is not a feature of Excel-it is entirely dependent on the printer driver being used. You can see if your printer driver will allow custom page sizes by displaying the properties dialog box for the printer (normally displayed by clicking Properties in the Print dialog box) and poking around in the various tabs and controls it contains.
In those cases where your printer driver allows you to define custom paper sizes and you are successful in defining one (or more), those paper sizes should appear within Excel without your need to do anything else. (Well, you may need to restart Excel or Windows after you create the custom paper size, but that will also depend on your printer driver and how it interacts with Windows.)
If your printer driver does not allow you to define a custom paper size, the only workaround is to use one of the paper sizes it provides. Pick a size that is larger than the custom size you would like to use, and then adjust the margins within Excel so that the resulting printable area on the page is the same as you would use on your custom paper size.