can i hep me with a grid

i want to do, something like this....

i use a grid 2*2

`
<Grid.RowDefinitions>


</Grid.RowDefinitions>
<Grid.ColumnDefinitions>


</Grid.ColumnDefinitions>

                                <Label Text="Forma de Pago:" Grid.Row="0" Grid.Column="0"/>
                                <Entry Grid.Row="1" Grid.Column="0"/>

                                <Label Text="Cuenta:" Grid.Row="0" Grid.Column="1"/>
                                <Entry Grid.Row="1" Grid.Column="1" />
                            </Grid>`

the problem is, the column take the size to label, and the second entry its very small because take the width at label, i need the entry take all width.
is there any way to column take all width?