You can have two approach:
1. You can bring all data with initial refresh and then filter the data with combo-box insertions. This way, the initial refresh may take more time, but subsequent filter actions from combo box will be faster.
2. Bring only the LOVs for the drop-downs during initial refresh (or hardcode LOVs in excel) and based on the values selected in combo-box, you can trigger refresh of the connection to fetch filtered data. This way, initial screen of dashboard will appear fast but subsequent filter actions from combo-box selections will be slower as it will hit the database every time the selection changes.
