Esta es para pintar un renglon completo!!!
Dim Ban As Boolean
Private Sub MSFlexGrid_Click()
If Not Ban Then
Poner_Color MSFlexGrid, MSFlexGrid.Row, vbYellow
Ban = True
MSFlexGrid.Row = MSFlexGrid.Row
MSFlexGrid.Col = 0
MSFlexGrid.SetFocus
Else
Quitar_Color MSFlexGrid, MSFlexGrid.Row, vbWhite
Ban = False
MSFlexGrid.Row = MSFlexGrid.Row
MSFlexGrid.Col = 0
MSFlexGrid.SetFocus
End If
End Sub

Sub Poner_Color(Flex As Control, Ren As Double, Color As Variant)
Dim LnCol As Double
With Flex
.Row = Ren
For LnCol = 0 To .Cols - 1
.Col = LnCol
.CellBackColor = Color
Next
End With
End Sub

Public Sub Quitar_Color(Flex As Control, Ren As Double, Color As Variant)
Dim LnCol As Double
With Flex
.Row = Ren
For LnCol = 0 To .Cols - 1
.Col = LnCol
.CellBackColor = Color
Next