In order to split an expense between multiple funding sources (deptids or grants) within e-Expense, you will need to follow specific instructions as detailed at http://finance.tufts.edu/accpay/files/eExpenseGuide.pdf#Split.
If you are using Firefox/Mozilla and you want to use the split expense feature you may receive a block message. To correct this problem, you'll need to disable protection for the page.
After clicking on the split button in e-Expense, click the "shield" logo in the URL window, as shown...
Next, click 'options' and disable protection for now.
Finally, click Resend. The page will reset itself - and you should then be able to use the split feature.