<script language="JavaScript"> <!-- function minusplus(y) { var x = 0; if ( document.plusminus.feld.value == "" ) x = "0"; else x = eval( document.plusminus.feld.value ); document.plusminus.feld.value = x + y; } function check() { var sal = document.plusminus.feld.value; var chkZ = 1; for(i=0;i<sal.length;++i) {if(sal.charAt(i) < "0" || sal.charAt(i) > "9") chkZ = -1} if(chkZ == -1) {document.plusminus.feld.value="1"} if(sal == "") {document.plusminus.feld.value="1"} } //--> </script> <div align=center> <form name="plusminus"> <input type="button" value=" - 1 " onclick="minusplus(-1)"> <input type="button" value=" - 10 " onclick="minusplus(-10)"> <input type="button" value=" - 50 " onclick="minusplus(-50)"> <input type="button" value=" - 100 " onclick="minusplus(-100)"><br> <input name="feld" type="text" size="25" value="1" onKeyUp="check()" style="text-align:center; font-weight:bold"><br> <input type="button" value=" + 1 " onclick="minusplus(1)"> <input type="button" value=" + 10 " onclick="minusplus(10)"> <input type="button" value=" + 50 " onclick="minusplus(50)"> <input type="button" value=" + 100 " onclick="minusplus(100)"> </form> </div>