Reversing the signs of selected cells - help neededddd

@Jindon. great buddy. thanks. one more thing - if I want to have my range defined in format "Cells(rowNo, colNo)", how will the syntax look like?? See my code below, in this case my colno I know. row no, i can change.. but how it will look like in syntax - For Each r In Range("C6,C10,C12") ???

Suppose I have a code like this -

Dim Datev As String

Datev = Sheets("hello").Cells(1, 10).Value
Datev = Mid(Datev, 4, 2)
'MsgBox (Datev)

colNo = 3
Do While Sheets("hello").Cells(11, colNo).Value <> Datev
colNo = colNo + 1
Loop

Dim r As Range
For Each r In Range("C6,C10,C12")
r.Value = Val(r.Value) * -1
Next
End Sub