While adding standard command button you can opt for SelectAll to mark all records in a form grid. However, there is no such a command for the opposite - unselect all records.
You can easily achieve it by using the following method and two usual button form controls.
[Form] public class myForm extends FormRun { public void selectAll(boolean _select) { VendPaymFormat_DS.markAllLoadedRecords(_select); } [Control("Button")] class FormButtonControlSelectAll { public void clicked() { element.selectAll(true); super(); } } [Control("Button")] class FormButtonControlUnSelectAll { public void clicked() { element.selectAll(false); super(); } } }