I want to manipulate data in excel with some complex functions.
It seems that I have to use VBA.
However I don’t want to learn it.
Is there any other way to do programming in the excel? Some language like C#?
I don’t want to create a independent C# application using some interface provided by Excel. Only program in excel, like VBA, but a different language.
You cannot unfortunately. To program in Excel from within Excel you will have to learn VBA.
To program for Excel, be it VBA, VSTO(C#, VB.Net) you need to understand the Excel Object Model (EOM) without which you cannot do programming for Excel.
You don’t need to learn VBA per se if you want to develop Office solutions from C# but as you become familiar with the EOM, you will notice that you automatically develop an understanding for VBA.
EDIT
Excel Object Model from Excel’s perspective
Excel Object Model Overview from VS’s perspective