You could use a User Defined Function that returned the value you wanted with passed parameters.

Bob

>I thought about that but i don't know how many groups1 i will have and i wanted to let the report to do the "dirty work" :)
>>Use report variables to sum weight and value, which can then be used in your footer to do the calculation.
>>
>>Bob
>>
>>>I have this problem with totals
>>>
>>>In a report with a kind of structure like this :
>>>
>>>group 1
>>>group 2
>>> month1 month2 month3 month4 . . . . . month12
>>>
>>>weight
>>>Value
>>>----------------
>>>group2 footer
>>>
>>>tot weight
>>>tot value
>>>-------------
>>>group 1 footer
>>>
>>>well, i can have the totals weight and value using the "calculate" function of reports, but i dont' know how to get the middle price sum(weight) / sum(value)
>>>
>>>How can i do ?