<script language ="javascript" type ="text/javascript">

function check_float(e,field)
    {
     if (!(((e.keyCode>=48)&&(e.keyCode<=57))||(e.keyCode==46)))
     {
        alert("Only Digits Are Allowed!");
        e.keyCode=0;                   
     }     
     if (e.keyCode==46)
     {
        var patt1=new RegExp("\\.");        
        var ch =patt1.exec(field);       
        if(ch==".")
        {
            alert("More then one decimal point not allowed");
            e.keyCode=0;
        }                        
     }
    } 
</script>

TextBox5.Attributes.Add("onkeypress", "check_float(event,document.getElementById('" + TextBox5.ClientID + "').value)");
        TextBox6.Attributes.Add("onkeypress", "check_float(event,document.getElementById('" + TextBox6.ClientID + "').value)");