The built-in UPS Real-Time method by default does not support an extra surchage. This can however be added through a simple modification to the file upsxmlrealinterface.asp. Please follow the guide below.
1) Open the file upsxmlrealinterface.asp using a text editor.
2) Locate the following line :
price=csng(price)
3) Modify the code above to :
price=csng(price) + 5
4) Save and close the file.
The code above will add an extra $5 surcharge to all the shipping rates returned by UPS. If you would like use percentage, you can use the following code :
price=csng(price) * 1.10
This will add a 10% surcharge to the shipping rates. For 15% use 1.15, 20% use 1.20 and so on.