The basic idea is make four (edit: oops, five) value queries, compose a table of all four, and compute columns 1, 1+2, 1+2+3, 1+2+3+4, then chart those series.
Step 1. Get the data
In a table dynamic property (preferably of a script element, as may be needed in step 2) make four sheets that query the four data points you're interested in.
Step 2. Compose the table
Do all four series have the same timestamps for their data?
a. If so, create a binding column (columns are created in the bottom left of a sheet) for each series on the sheet with query 1, and bind in those columns. The easiest way to do this is to bind the table in the dynamic properties list to the field labelled 'source table' and use the drop downs.
b. If not, consider writing a script to transpose the values to the correct rows in a fifth table. You can do this by getting the table rows, as documented at dglogik's wiki: http://wiki.dglogik.com/dglux_v2_wiki:dgscript, looping and doing the summing/transposing. I can provide more detail if necessary.
Step 3. Compute
Create three formula columns, and use these to sum the values appropriately. For a formula column script, the name of the column corresponds to the value in that column in that row. So, your scripts will look like "return A+B;" and return "A+B+C" although you may need the parseFloat() function.
Step 4. Chart
Click, drag and bind each data series to the chart. Configure their colors and tooltips so that you know which is which, and be sure to give each series a meaningful label. If they are ordered improperly, and one of the larger sums is displayed on top, you can re-order the series in the 'special' subdivision of each 'series' group on a chart element.
Hope that helps :D