change the 8th column in a not contiguous array

i have this code, that selects a range which may be contiguous, or not
depending on what you select in the listbox.

Private Sub OKButton_Click()

Dim RowRange As Range
Dim Rng As Range
Dim RowCnt As Integer
Dim r As Integer

RowCnt = 0
For r = 0 To ListBox1.ListCount - 1
If ListBox1.Selected(r) Then
RowCnt = RowCnt + 1
If RowCnt = 1 Then
Set RowRange = Range("MyRange").Rows(r + 1)
Else
Set RowRange = Union(RowRange, Range("MyRange").Rows(r + 1))
End If
End If
Next r
If Not RowRange Is Nothing Then RowRange.Select
Unload Me

End Sub


what can i add to it to make it change the 8th column to the value "A" in
the selected ranges only?

TIA