How To Divide Excel Sheet Vertically Into 4 Parts

I have many excel sheets with 1000 columns and 100,000 rows. I have to import these sheets into SAS system which wont let me import more than 250 columns per sheet (it misses the remaining columns, though rows it can import all of them). So, one solution is break each such sheets into 4 individual sheets. Ofcourse I can manually take the cursor to 250th column and copy/paste that data into another sheet and so on. But this is cumbersome and also means there is chance of mistake.

Is there a way I can divide the sheets into 4 sheets separately with each sheet having equal number of columns? Another thing I need to do is that on the top row there are company codes -most of them start with a letter which is fine. There are few which start with a number and I have to add a dummy letter x before the number. Now since there are 1000 columns, I have to scan the top row of all 1000 columns to find number codes which are scattered unevenly. So I was wondering if there is a way to tell excel to change all such number codes with extra x behind each number?