var oField = crmForm.all.SOME_FIELD_ID;
// Toggle the disbled state of the field
oField.Disabled = !oField.Disabled;

var CRM_REQUIRED_LEVEL_NORMAL = 0;
var CRM_REQUIRED_LEVEL_RECOMMENDED = 1;
var CRM_REQUIRED_LEVEL_REQUIRED = 2;
var oField = crmForm.all.SOME_FIELD_ID;

switch (oField.RequiredLevel)
{
   case CRM_REQUIRED_LEVEL_NORMAL:
      alert("This field is not required or recommended");
      break;

   case CRM_REQUIRED_LEVEL_RECOMMENDED:
      alert("This field is business recommended");
      break;

   case CRM_REQUIRED_LEVEL_REQUIRED:
      alert("This field is required");
      break;
}

var oField = crmForm.all.SOME_FIELD_ID;

if (oField.IsDirty)
{
   alert("The field's value has changed.");
}
else
{
   alert("The field's value has not changed.");
}

// Set focus to the field.
crmForm.all.SOME_FIELD_ID.SetFocus();

// Set focus to the field.
crmForm.all.SOME_FIELD_ID.FireOnChange();