You will have to open the file in one way or another if you want to access the data within it. Obviously, one way is to open it in your Excel application instance, e.g.:-
(untested code)
Dim wbk As Workbook
Set wbk = Workbooks.Open("C:\myworkbook.xls")
' now you can manipulate the data in the workbook anyway you want, e.g. '
Dim x As Variant
x = wbk.Worksheets("Sheet1").Range("A6").Value
Call wbk.Worksheets("Sheet2").Range("A1:G100").Copy
Call ThisWorbook.Worksheets("Target").Range("A1").PasteSpecial(xlPasteValues)
Application.CutCopyMode = False
' etc '
Call wbk.Close(False)
Another way to do it would be to use the Excel ADODB provider to open a connection to the file and then use SQL to select data from the sheet you want, but since you are anyway working from within Excel I don't believe there is any reason to do this rather than just open the workbook. Note that there are optional parameters for the Workbooks.Open() method to open the workbook as read-only, etc.