Accumulate the values to get an increasing line chart

Hi,

I have a database in which we log at around every 15 minutes the number of tablets produced. I have a date and a qunatity.

We would need to see a line chart that accumulates the values, generating an increasing line.

For Example:

At 6.30 we start from 0

At 6.45 we produced 10.000 tablets

At 7.05 we produced another 12.000 tablets

At 7.30 we produced another 16.000 tablets.

My data looks like this

Date&Time    Qunatity

6.30                   0

6.45                 10.000

7.05                 12.000

7.30                 16.000

On the line chart I would like to se ponits at the following values:

At 6.30 : 0

At 6.45 : 10.000

At 7.05 : 22.000 (10.000+12.000)

At 7.30 : 38.000 (10.000+12.000+16.000)

Thank you,

Nandor