SUM without constant 'period'

[24hrclock@xxxxxxxxxxxxx]

I am playing around with some tick data and wonder if the following is 
possible:

Can I somehow get the SUM of the tick-prices over a 1-minute period?

I can easily determine the number of ticks in the preceding minute and 
assign that value to a variable, however, the function "Sum(array,period)" 
will only except a constant (not a variable) for 'period'. And of course 
logical do/while loops are out of the question ;-)

Have I hit a brick wall, or simply need more "MS outside the box" formula 
perspective?

Thanks in advance,

24h