Percentual no FlexGrid

Na coluna 03 do FlexGrid carrego os valores para cada linha. Preciso calcular o percentual de cada linha e apresentar na coluna 04 do Grid. Esse calculo é feito pegando o valor da linha da coluna 03 e dividindo pelo valor destacado em um TextBox e apresentando na linha da coluna 04. Como faço isso? Por favor!!

Private Sub PreencheGrid()
GerarValores
Grid.Redraw = False
Grid.Rows = 1
Dim Row As Integer
Dim i
Set TbResumo = New ADODB.Recordset
If TbResumo.State = 1 Then TbResumo.Close
With TbResumo
.CursorType = adOpenStatic
.CursorLocation = adUseClient
.LockType = adLockPessimistic

	.Source = "SELECT OS FROM Dados GROUP BY OS ORDER BY OS"
	.ActiveConnection = BancoSobra
	.Open

	If .BOF = True And .EOF = True Then Exit Sub

	Grid.Rows = .RecordCount + 1
	'Row = 0
	Do Until .EOF = True
 Row = Row + 1
 Grid.Col = 0

 Grid.Row = Row
 Grid.TextMatrix(Row, 0) = !OS

Set TbCliente = New ADODB.Recordset
With TbCliente
.CursorType = adOpenStatic
.CursorLocation = adUseClient
.LockType = adLockPessimistic

	.Source = "SELECT Cliente,Numero,Descricao FROM DadosCT WHERE Numero = '" & TbResumo("OS") & "' ORDER BY Cliente,Numero,Descricao"
	.ActiveConnection = BancoSobra
	.Open

Do Until .EOF = True
Grid.TextMatrix(Row, 1) = !Cliente
Grid.TextMatrix(Row, 2) = !Descricao

Set TbGasto = New ADODB.Recordset
With TbGasto
.CursorType = adOpenStatic
.CursorLocation = adUseClient
.LockType = adLockPessimistic

	.Source = "SELECT Sum(Quant*Unit) AS Total FROM Dados WHERE OS = '" & TbCliente("Numero") & "'"
	.ActiveConnection = BancoSobra
	.Open

Do Until .EOF = True
Grid.TextMatrix(Row, 3) = Format(!Total, "#,##0.00")

.MoveNext
Loop
End With

.MoveNext
Loop

End With

TbResumo.MoveNext
Loop
End With

Grid.Redraw = True
Grid.Row = 1
Grid.Row = Grid.FixedRows
Grid.TopRow = Grid.FixedRows
Grid.Row = Grid.TopRow
Grid.Col = 1
Grid.ColSel = Grid.Cols - 1
End Sub