If Load statement

[YanMin]

Hi, 

Can anyone help me with following if load statement. My files got different column names. So what I want to do is after certain date, I want load different column name. My codes is as follows: 

if(Date(right(FileBaseName(),8))<Date('20210405'),

"Wishlist Visitor","Wishlist Visitors") as "Wishlist Visitor",

The spelling of column name is different for the files that is before that specific date. That codes seems no work.

Can anyone help?

Thanks in advanced

[YanMin]

Well noted.

Thank you sir