Remove symbol from flat fileduring data load

I have a huge text file which has square symbol on it and getting data load error, message no. BRAIN 290 which is data conversion error for invalid characters during ODS (BW object) activation.

Just wondering how to clean this square invalid characters in transfer rule?

I can't fix in the source and don't want to fix in flat file but in Transfer Rule using code.

I need help in writing code. What command will it be to check the square symbol and remove? there is no fix position. In each record, symbol is in different position.

See the link to understand the data: http://www.erpmastering.com/Document1.pdf

Thanks.