how to import an excel sheet in a dynamic nav

Using Excel Buffer Table.
I would create a ProcessingOnly report in which I would insert Integer as DataItem and place a FOR loop in OnAfterGetRecord(). In OnPreDataItem you must call OpenBook and ReadSheet functions on ExcelBuffer.
In there you can define a variable that will check for how many rows there are in your Excel sheet and one that will allow you to enter manually from which row you want to start importing.
Then you simply use GET on excel buffer to get wanted cell and then just validate that value to your NAV record using Cell Value As Text from Excel Buffer.