How to create grid with squares

[Petrarca181]

Hello, this is my grid.

<Grid
    x:Name="myGrid"
    RowSpacing="10"
    ColumnSpacing="10"
    Margin="10"
    ColumnDefinitions="*,*,*"
    RowDefinitions="*,*,*"
    VerticalOptions="Fill"
   >

Grid may have undefined number of colums and rows. What I want is after grid is loaded and column sizes are calculated to set height of every row equal to first colm witdh. Have no idea how to realize this in maui.