Expression Editor/Builder in Screens

Hi,
I am working on Formula Editor/Expression Builder in new Custom Screen by taking the reference of Base Acumatica screen  Allocation Rules(PM207500)  Quantity Formula field.

In ASPX there is a syntax like below
                                    <pxa:PMFormulaEditor ID="edQtyFormula" runat="server" DataSourceID="ds" DataField="QtyFormula" Parameters="@Rate,@Price" />

How can we approach these type of Selectors in our Custom Screens? 
Any Steps to follow, Suggestions/Test case will be helpful.

Thanks.