You should be able to use something like 
Sheets("LVL1 GRAPH DATA").Range("F7").End(xlDown)
If all the data starts in the same place you should be able to use this to find the bottom of a range if there are no blanks.

If you have a sheet that has no data, you will have to trap that out first. 

Sheets("LVL1 GRAPH DATA").Range("F7").Value = "" Then
     ''Do Nothing
End If