What would be the criteria to split on?
Do we just count 400 lines and put it in another sheet?
Is the data sorted or do we need to search for all of the data?
Do you have a sample worksheet with all of the personal/confidential data removed?
Is the data going to go in another workbook or will the current workbook suffice?
Are the sheets added or are they already existing?
How are the sheets named or do we name them and how (so far as the name) or does it matter?