Create Custom Function

Hi,
can we make our own or you may say i.e, custom function.

suppose a formula i.e, =sum(A1:F1) and we define the name for the formula "xyz".

My question is if we put the formula "xyz" in any workbook of different Excel file, than it calculates sum of the above range either absolute or relative reference.

summery of question : How to record of custom formula

You would need to put the UDF in an addin.

Thanks for suggestion. But sir, I can not find in Excel Option---->Add-Ins--->Manage Excel Add-ins. I request you, please suggest how to install.

You need to create a new workbook, add the UDF, save it as an addin, then get your people to install it http://office.microsoft.com/en-gb/excel-help/add-or-remove-add-ins-HP010342658.aspx