Or use the Rate function:

=rate((today()-date(2,5,2))/365,0,-1000,1500)

--
Regards,
Fred


"Duke Carey" wrote in message
...
=(1500/1000)^(1/((TODAY()-DATE(2002,5,2))/365))-1

or just under 11%

"Stephen Watson" wrote:

If an investment of say £1000 was made on 02/05/02 and is now worth £1500
today.

What is the formula I need to work out the % I would have needed to invest
the money at had the amount been invested at a guaranteed rate.

Thanks