If you really need the formula approach, but don't want to have to recopy each day then you can always add a null qualifier to your existing formula, I.E. =IF([jpmemail.xls]Sheet1!A1="","",[jpmemail.xls]Sheet1!A1).
Substitute my example for whatever your actual formula is and then copy in your reference workbook for as many cells as you've ever had maximum data from the JP Morgan e-mail.
Note that this method will affect recalculation times vs. the
VB approach.
Hope that helps,
Smitty