Multiply Decimal values in JavaScript example

Hi,

i have three textboxes in my page to multiplication like

Quantity*Rate*INR Rate = Total Amount (result is coming)

suppose if i typed decimal points in rate textbox should calculate in Total amount by using javascript.

function Calculate() {

            var txt1 = document.getElementById('<%= txtqty.ClientID%>').value;
            var txt2 = document.getElementById('<%= txtrate.ClientID%>').value;

            var conversion = document.getElementById('<%= ddlcurrency.ClientID%>').value;

            if (conversion != "1") {
                document.getElementById('<%= tdInrConversion.ClientID%>').focus();
                var txt3 = document.getElementById('<%= txtInrConversion.ClientID %>').value;
            }
            else
                var txt3 = ''

            if (txt1 != '' && txt2 != '' && txt3 != '')
                document.getElementById('<%= txtamount.ClientID%>').value = eval((parseInt(txt1) * parseInt(txt2) * parseInt(txt3)));
            else if (txt1 != '' && txt2 != '')
                document.getElementById('<%= txtamount.ClientID%>').value = eval((parseInt(txt1) * parseInt(txt2)));
            else
                document.getElementById('<%= txtamount.ClientID%>').value = 0
        }