Numeric and Range Validation for Multiple TextBoxes using JavaScript

HI

I have 3 textbox in my page I want use Numeric limit for them I use below code before for 1 textbox

     <script type = "text/javascript">
         function isNumeric(keyCode) {
             var r = ((keyCode >= 48 && keyCode <= 57) || keyCode == 8 ||
                (keyCode >= 96 && keyCode <= 105))
             if (!r) {
                 alert("please enter number");
             }
             return r;
         }
         function ValidateRange() {
             var value = parseInt(document.getElementById("<%=txtNumeric.ClientID%>").value);
             if (value < 1000 || value > 9000) {
                 alert("please enter number between 1000-9000");
                 return false;
             }
         
             return true;
         }
    </script>

now I want use above code for 3text box How I can do it?

I should write different script for each textbox?

can I use just 1script for all textbox?

Best regards