How to tell if a form was opened with 'Go to main table' function

I found this sample code really helpful in connection with a customization,where the customer wanted to alter the 'Go to main table' function.

Respect to original poster (though I can't remember where I found it - but the idea is not mine)

On main datasource:
public void executeQuery()
{
query q;
querybuilddatasource qbds;
querybuildrange qbr;
int fldLookupField;
str sLookupValue;
;
if ( element.args().caller() &&
!element.args().dataset() &&
element.args().lookupField() &&
element.args().lookupValue()) //jumpref
{
sLookupValue =element.args().lookupValue();
fldLookupField =element.args().lookupField();

q=this.query();
qbds=q.dataSourceTable(this.table());
qbr=qbds.addRange(fldLookupField);
qbr.value(sLookupValue);
this.query(q);
}
super();
}