You need to add a GuiTextListCtrl within the GuiScrollCtrl, and then you can use:
GuiTextListCtrl.addRow(int id, string text, int index=0)
to add text to the control.
Example:
function GuiControl::onWake(%this)
{
GuiTextListCtrl.clear();
for(%i = 0; %i < DataBlockGroup.getCount(); %i++)
{
%obj = DataBlockGroup.getObject(%i);
if(%obj.getClassName() $= "ItemData" && %obj.uiName !$= "")
GuiTextListCtrl.addRow(%i, %obj.uiName);
}
}
Where GuiControl is the name of the Gui, onWake is the function called when the Gui is opened, and GuiTextListCtrl is the name of the Text List.