How to set value in coc Validate method D365?

Question

In Dynamics D365 FFO, I would like to set the value in VALIDATE chain of command method.

My Code:

[ExtensionOf(formDataFieldStr(MyFORM,MyDataSource, MyControl))]
final class MyFORM_MyDataSource_MyControl_Extension
{    
public boolean validate()
{
    boolean                  ret;
    FormDataObject           formDataObject;
    FormDataSource           formDataSource;
    MyTable                  currentMyTable;
    MyEDTField_CurrentRecord myEDTField_CurrentFIELD;

    ret = next validate(); 

    formDataObject = any2Object(this) as FormDataObject;
    formDataSource = formDataObject.datasource();

    currentMyTable           = formDataSource.cursor();
    myEDTField_CurrentFIELD  = currentMyTable.MyField;

    if("MyLogic.... - myEDTField_CurrentFIELD ")
    {
        ret = checkFailed("KO");
      
        *// I WOULD LIKE TO SET BLANK VALUE FIELD HERE*
    }
    return ret;
}

Is it possible to call and set the value field in Chain of command method Valitdate. If validation is KO, I need to set null value.

Thanks