XFGetCell is an Excel function that goes to OneStream and retrieves a number. It doesn't know anything about CubeViews.
What you probably want is XFGetDashboardParameterValue. From the page "Retrieve Function" in Design and Reference Guide:
This function is available to Excel Add-in and Spreadsheet. If that function is used within an XLSX file that is using a function like XFGetCell or XFSetCell (or similar) where these are referencing a custom parameter value (e.g. ParamEntity) that is on the Dashboard that references this Spreadsheet from within it as a Component. The practice to get this Custom Parameter value is to use XFGetDashboardParameterValue to fetch the text from that Parameter or its default value and place it in a cell on the Spreadsheet (e.g. B1). Then the cell that is using a retrieve function such as XFGetCell would reference this other cell (i.e. B1).
XFGetDashboardParameterValue("myParamName", "Text For Default Value")
