I am trying to write a For Loop which runs all the populated cells in the
range through a calculation. My question is how do I make sure that empty or
null cells aren't selected to be used in the calculation? Essentially I just
want to ignore the empty/null cells. Below is the code for the loop in case
this helps:

For Each A In range1
For Each B In range1
If B.Value < A.Value Then
If Abs(A - B) <= testvalue Then
Sheets("Test Results").Select
range("A1").Select
Selection.End(xlDown).Select
ActiveCell.Offset(1, 0).Select
Selection.Value = "Interference"
ActiveCell.Offset(0, 1).Select
Selection.Value = A.Value
ActiveCell.Offset(0, 1).Select
Selection.Value = B.Value
End If
End If
Next
Next