function keypress_number(decimal) {
  var keypressed = window.event.keyCode;
  var ElementText  = window.event.srcElement.value ;
  
  temp = "" + ElementText; // temporary holder

while (temp.indexOf('.')>-1) {
pos= temp.indexOf('.');
temp = "" + (temp.substring(0, pos) + '1' + 
temp.substring((pos + '.'.length), temp.length));
}
  ElementText = temp; 
  
  if (keypressed == 45){
    if (ElementText.length!=0) {
      window.event.keyCode = 0;
    }
    
  }
  else {
    if (decimal) {
      var Reg = /\./g;
      if (Reg.test(ElementText)) {
        if( (keypressed >= 48 && keypressed <= 57) == false) {
          window.event.keyCode = 0;
        }
      }
      else {
        if ((keypressed >= 48 && keypressed <= 57 || keypressed == 46) == false) {
          window.event.keyCode = 0;
        }
      }
    }

    else {
      if ((keypressed >= 48 && keypressed <= 57) == false) {
        window.event.keyCode = 0;
      }
    }
  }
}