For a Single map: Name each of the supply dock/pile/warehouse(s) a specific name (such as supply001) using the object property box in worldbuilder, then go into scripts (edit->scripts) and find something near the lines of 'Change cash amount for a warehouse' (if you were using Zero Hour I could be more specific.) Then insert the correct info (Supply thing name, cash amount) and do this for every supply thing you want to change.


For The whole Game (modding):
use FinalBig to extract from C:\Program Files\EA Games\Command and Conquer Generals\INI.Big and extract "Data\INI\CivilianBuilding.ini" to anywhere (preferably an easy-access place such as your desktop), and open it up. Use Ctrl+F to find ' StartingBoxes ' And change the value. 50 = $3,500 in supplies and 400 = $60,000; so I'm not sure if this is the correct code, but you should try it out. 60k/400=150(1 = $150) and 3.5k/50=70(1 = $70) so I'm a little confused on this one.

Keep in mind that setting the StartingBoxes value won't change the number of boxes (and the initial amount of cash) for Supply Docks whose capactities are set in the map. If the starting value of the Supply Dock is anything other than 30,000 then you can't change the value with INI code.