onOpen example
The following onOpen event handler adds a calculated field to a query.
function invoice1_onOpen( )
c = new Field( )
c.fieldName := "Total"
this.rowset.fields.add( c )
c.beforeGetValue := {||this.parent["Qty"].value * this.parent["PricePer"].value}
Note that the this in the second statement refers to the query, but in the codeblock, this refers to the calculated field.