Excel 2007 : Formula to leave first 3 words in sentence and delete the rest?

Hello,

What formula can i use to leave only the first 3 words from a text in cell and delete the rest of the words? For example, from this text:

monday is the first day of the week
the third planet of the solar system is the Earth

i want to get this result:

monday is the
the third planet


Thanks!

Try:

=TRIM(LEFT(SUBSTITUTE(A1," ",REPT(" ",100)),300))