You can directly access some files. I use the below to access our .xls spreadsheets:
Add a file to Quality Center Resource Folder (must be in .xls format, not .xlsx). For  the below example, I created an Excel (.xls) file with one worksheet named Step1, two columns and two rows:
    [ A      ][ B      ]
    [ Value1 ][ Value2 ]
    [ a      ][ cash   ]
Save it as .xls, upload to Resource path of 
    ResourcesQTP ResourcesDataTest
Then here is the sample code to access it (Make sure QTP/UFT has an active connection to QC):
    Datatable.AddSheet ''newSheet''
    Datatable.ImportSheet  ''[QualityCenterResources] ResourcesQTP ResourcesDataTest'', ''Step1'', ''newSheet''
    msgbox Datatable(''Value1'', ''newSheet'')
    msgbox Datatable(''Value2'', ''newSheet'')