Help with text boxes

Hi Friend,

Below function help your enter only decimal value in textbox.
/*****************************************************************************
10.This function is used to Check for Currency entry  in Textbox/Textarea/select box for the Empty,
Maximum value
Note1:If Required is set to false,then it validates only if you enter in the
input boxes.
Ex: fnCheckCurrency("document.frmAddEdit.txtCurrency","Amount","99999999.99",true);   
******************************************************************************/

/************************ UPDATED BY CHITAL ON 31st October, 2006 ****************************/
function fnCheckCurrency(ObjectName,ObjectCaption,MaxVal,Required){
    var strErr = ""
    ObjectName=eval(ObjectName)
    if(ObjectName.value.substring(0,1) == "$")
    {
        ObjectName.value=ObjectName.value.substring(1,ObjectName.length);       
    }
   
    if(ObjectName.value == "0.00"){
        l = 0;
    }else{
        l = ObjectName.value.length;
    }
    if (Required==true ||(Required==false && l>0)){
       
        if(ObjectName.value.length <=0)
        {
            ObjectName.value=0;
        }
        else
        {   
            var curEntered = ObjectName.value;
            if (isNaN(curEntered)||fnIsEmpty(curEntered)){               
                strErr = ObjectCaption + " " + strErrValidCurrency + " \n\    " ;
            }
            else if (curEntered < 0){
                strErr = ObjectCaption + " " + strErrNegativeValue + " \n\    " ;
            }           
            else{
                curEntered = parseFloat(curEntered)
                    if (curEntered > MaxVal){
                    strErr = ObjectCaption + " " + strErrExceed + " " + MaxVal + " \n\    " ;
                }   
            }       
        }
        if (strErr != ""){
            strErrMessage = strErrMessage + strErr;
            if ((objFocus == undefined)||(objFocus == "")){
                objFocus = ObjectName
            }
        }       
    }else{return true;}
}

result = (1-(N/M)*100;// old code

 result = Math.Sqrt(result);// new code

textBox5.Text = result.ToString();// old code that is all

ok now is the continious with program.
i must  sqrt finish result?
how to do that?

thank you.
my program is working.

Thanks for your helping but it does not work. try it in your program
a = 16
b = 42
c = 17
d = 41

result in textbox.5 must be 8.12 %

Here is the screen shot. What i must type in to declare variables.
thanks for answer.
here is the ss
http://img160.imagevenue.com/img.php?image=23219_kako_122_1103lo.JPG