label is not displaying text in runtime

i have a grid inside i have 3 bound columns
1.empid
2.empno(editable)
3.empname
 
empno should allow only 20,21 ,if i enter not 20,21 then i want to show error message

dim x as boolean=false
so in row updating event
if(empno==20 ||empno==21)
{
   //implementation
   x=true
}
if(x=false)
{
   lblmessage.text="please enter 20,21."
}

problem is lblmessage is was not displaying the text in runtime. please help me