Make sure your record sort is on the ID field

 

in addition to this question is it possible to do a count like this over a given fixed value ?

 

like

 

Data1    10550

Data1    450

Data1    300

Data1    200

Data2    900

Data2    300

Data2    100

 

so do that count of the first record - the second - the 3e until the date changes

 

so for example if grouped on date it gives for data1  9600

and for Data2 500

 

Tnx already !!

DBlank asked for me to help you out with shared variables as this is a method to accomplish what you are looking at.

 

Shared variables usually involve 3 formulas, 1) to initialize the variable (usually 0, but not in this case), 2) increment the variable, and 3) display the results.  In your case they would look something like:

 

in the group header, initialize:

shared numbervar counter := 0;  //on second thought, this might be better

""  //to hide the formua's output, you could supress the formula (I think)

 

in the detail section:

shared numbervar counter;

if counter = 0 then

  counter := {table.field}

else

 counter := counter - {table.field};

""  //again to hide the output (remove this line for debugging)

 

in the group footer:

shared numbervar counter

 

 

this can also be used for the differencing if desired with but a few modifications, but if something is working, why mess with it ;)

 

HTH