I managed to place the docked bar, in my Stylesheet, using the following expression:
CreateDocument[
Notebook[{Cell[StyleData[StyleDefinitions -> "Default.nb"]],
Cell[StyleData[All, "Working"],
DockedCells ->
Cell[ToBoxes[ExpressionCell[set1]], "DockedCell",
Background -> "None"]]},
StyleDefinitions -> "PrivateStylesheetFormatting.nb"]]
Where, set1 is the grid containing the set of buttons.
Thanks again.