VBA/Excel/Access/Word/Data Type Functions/IsNumeric

Is the cell numeric

 
Sub ResetTest2()
    For Each n In Range("A1:A8")        "   Substitute your range here
        If IsNumeric(n) Then
            n.Value = 0
        End If
    Next n
End Sub

Use IsNumeric to check the input value

 
Sub EnterSquareRoot3()
    Dim Num As Variant
    Num = InputBox("Enter a value")
    If Not IsNumeric(Num) Then
       MsgBox "You must enter a number."
       Exit Sub
    End If
    If Num < 0 Then
        MsgBox "You must enter a positive number."
        Exit Sub
    End If
    ActiveCell.value = Sqr(Num)
End Sub