In SQL reporting, How do I add the formula in the Formula bar?

All the data is coming from a

You have to write SSRS expressions Go through below link

https://msdn.microsoft.com/en-IN/library/ms345237.aspx

I am doing all the calculations in SQL, but they want to see the formula in the formula bar in excell

Hi Helix, 

According to your description, you want to see the expression in the excel file after exporting to excel, right? 

In Reporting Services, text box values that are expressions are not converted to Excel formulas. It's because the text box values evaluated during report processing and the evaluated expression is exported as the contents of each Excel cell. This work mechanism is by design. So for your requirement, it cannot be achieved currently. 

Reference: 

Exporting to Microsoft Excel (Report Builder and SSRS)

If you have any other question, please feel free to ask. 

Regards,
Shrek Li