如何在Excel VBA中循环范围内的列

The title may be similar to other questions but as far as I can tell no one has asked this one. I am trying to loop through all columns and add the sum of them at the bottom after the last row and make the values before the sum grey. Up until this point I have been writing out each column name but the sheets keep getting larger and this is becoming a waste of time because I know there must be a better way. Please keep in mind I am new to VBAs. The section of the code is:The title may be similar to other questions but