Either remove the parentheses
rs_store.Open "SELECT store_exp.type, Sum(store_exp.amount) AS SumOfamount, First(store_exp.[amt type]) AS [FirstOfamt type] From store_exp GROUP BY store_exp.type", cn
or pass all parameters including the optional ones enclosed by parentheses:
rs_store.Open("SELECT store_exp.type, Sum(store_exp.amount) AS SumOfamount, First(store_exp.[amt type]) AS [FirstOfamt type] From store_exp GROUP BY store_exp.type", cn, adOpenForwardOnly)