For periods 1 to (say) 12:
=25000+CUMPRINC(7.25%/12,15*12,25000,1,12,0)
Returns: 24042.5099593359
Which is the balance outstanding after the 24th payment.
Or without Analysis ToolPak:
=FV(7.25%/12,12,PMT(7.25%/12,15*12,25000,0,0),25000,0)
Returns: -24042.5099593359
Which is the obligation (-) at the end of the 12th period.
There's a CUMPRINC function (part of the Analysis Tool Pak -- Help tells you
how to install it if necessary) that will calculate the cumulative principle
paid between two periods that you specify. Subtracting that from the initial
principal would give you the balance. See Help for information on the
arguments and pay particular attention to the examples. With monthly payments,
the rate is the APR/12, the period is the month number, etc.