As long as each xlsx is set up the same way, just iterate over a list of the files:
 
FPlist = {"$DESKTOP/temp.xlsx", "$DESKTOP/temp1.xlsx"};
For Each( {val}, FPlist,
	Open(
		val,
		Worksheets( {"Sheet1", "Sheet3"} ),
		Use for all sheets( 1 ),
		Concatenate Worksheets( 0 ),
		Create Concatenation Column( 0 ),
		Worksheet Settings(
			1,
			Has Column Headers( 1 ),
			Number of Rows in Headers( 1 ),
			Headers Start on Row( 1 ),
			Data Starts on Row( 2 ),
			Data Starts on Column( 1 ),
			Data Ends on Row( 0 ),
			Data Ends on Column( 0 ),
			Replicated Spanned Rows( 1 ),
			Suppress Hidden Rows( 1 ),
			Suppress Hidden Columns( 1 ),
			Treat as Hierarchy( 0 ),
			Multiple Series Stack( 0 ),
			Import Cell Colors( 0 ),
			Column Separator String( "-" )
		)
	)
);