VBA loop to multiply by negative one

Hello
I have put something together, just for the initial column calculation. Please expand on the moving across the columns.
Also do you know how much data is available as my initial loop stops after a blank value so we need to try a different logic there.

Sub test()
    Range("A2").Select
    myvalue = ActiveCell.Value
    While myvalue <> ""
        Ignore = False  'used to check whether there are valid values or not
        If myvalue < 0 Then
            factor = 1
        ElseIf myvalue > 0 Then
            factor = -1
            Else: Ignore = True  'where it is blank or N/A
        End If
        
        If Ignore = False Then  'we need to do something
            For n = 1 To 5
                ActiveCell.Offset(n, 24).Value = factor * ActiveCell.Offset(n, 11).Value
            Next n
            ActiveCell.Offset(n - 1, 0).Select
        End If
        ActiveCell.Offset(1, 0).Select
        myvalue = ActiveCell.Value
        If IsError(myvalue) Then myvalue = 0
    Wend
End Sub

Regards