Sorry can't help with VB but this is how I would do it in JavaScript..
var List = ["C:\\","G:\\","I:\\"];
scratchDisk(List);
function scratchDisk(List) {
var desc = new ActionDescriptor();
var ref = new ActionReference();
ref.putProperty( charIDToTypeID('Prpr'), charIDToTypeID('CchP') );
ref.putEnumerated( charIDToTypeID('capp'), charIDToTypeID('Ordn'), charIDToTypeID('Trgt') );
desc.putReference( charIDToTypeID('null'), ref );
var desc2 = new ActionDescriptor();
var list = new ActionList();
for(var a in List){
list.putString( List[a]);
}
desc2.putList( charIDToTypeID('ScrD'), list );
desc2.putUnitDouble( charIDToTypeID('MmrU'), charIDToTypeID('#Prc'), 70.000000 );
desc.putObject( charIDToTypeID('T '), charIDToTypeID('CchP'), desc2 );
try{
executeAction( charIDToTypeID('setd'), desc, DialogModes.NO );
}catch(e){}
};
