Калькулятор, способный выполнять сразу несколько действий

<CENTER>
<FORM NAME="Calc">

<TABLE BORDER=4>
<TR>
<TD>
<INPUT TYPE="text" NAME="Input" Size="16">
<br>
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE="button" NAME="one" VALUE=" 1 " OnClick="Calc.Input.value += '1'">
<INPUT TYPE="button" NAME="two" VALUE=" 2 " OnCLick="Calc.Input.value += '2'">
<INPUT TYPE="button" NAME="three" VALUE=" 3 " OnClick="Calc.Input.value += '3'">
<INPUT TYPE="button" NAME="plus" VALUE=" + " OnClick="Calc.Input.value += ' + '">
<br>
<INPUT TYPE="button" NAME="four" VALUE=" 4 " OnClick="Calc.Input.value += '4'">
<INPUT TYPE="button" NAME="five" VALUE=" 5 " OnCLick="Calc.Input.value += '5'">
<INPUT TYPE="button" NAME="six" VALUE=" 6 " OnClick="Calc.Input.value += '6'">
<INPUT TYPE="button" NAME="minus" VALUE=" - " OnClick="Calc.Input.value += ' - '">
<br>
<INPUT TYPE="button" NAME="seven" VALUE=" 7 " OnClick="Calc.Input.value += '7'">
<INPUT TYPE="button" NAME="eight" VALUE=" 8 " OnCLick="Calc.Input.value += '8'">
<INPUT TYPE="button" NAME="nine" VALUE=" 9 " OnClick="Calc.Input.value += '9'">
<INPUT TYPE="button" NAME="times" VALUE=" x " OnClick="Calc.Input.value += ' * '">
<br>
<INPUT TYPE="button" NAME="clear" VALUE=" c " OnClick="Calc.Input.value = ''">
<INPUT TYPE="button" NAME="zero" VALUE=" 0 " OnClick="Calc.Input.value += '0'">
<INPUT TYPE="button" NAME="DoIt" VALUE=" = " OnClick="Calc.Input.value = eval(Calc.Input.value)">
<INPUT TYPE="button" NAME="div" VALUE=" / " OnClick="Calc.Input.value += ' / '">
<br>
</TD>
</TR>
</TABLE>
</FORM>
</CENTER>