If the games are saved with AGS's standard save game system, use GetSaveSlotDescription() instead. Eg:
If you want to enter text directly into a label, I think the only way is to make it into a textbox. However, as you want 4 of such labels at the same time that can cause problem, my suggestion is to provide buttons to save to eact slot, when you click a button, it'll prompt you for the description.
if (GetSaveSlotDescription (1, saveslota)) SetLabelText (11, 4, saveslota); else SetLabelText (11, 4, "EMPTY");
If you want to enter text directly into a label, I think the only way is to make it into a textbox. However, as you want 4 of such labels at the same time that can cause problem, my suggestion is to provide buttons to save to eact slot, when you click a button, it'll prompt you for the description.