Hello,
Onchange event set following code
protected void txtDays_TextChanged(object sender, EventArgs e)
{
int numdays = 0;
if (txtDays.Text != "")
{
numdays = Convert.ToInt32(txtDays.Text);
}
if (numdays > 15)
{
string strimsg = "Number is Exceeds 15 Days";// Set Your OWN message here
string strJavaScript = "<script language = javascript type=text/Javascript> alert('" + strimsg + "')</script>";
this.Page.RegisterClientScriptBlock("Key4", strJavaScript);
}
}
Hope this is helpful !
Thanks