Help in displaying the text on a button in a textbox

Hello, for my project I have a part where a user is required to click the chosen text button and the text written on the button will appear in a textbox. But my coding makes it hard if more than 5 text buttons are created. Is there any easier way?
ps: it would be easier if I can show you guys my screen, but I cannot see any upload from the Insert/Edit Image icon.
This is my code:
<----------HTML------> <table width="100%" align="center"> <tr> <td width="20%" align="center"><br /> <asp:Button ID="king" CssClass="button1" OnClick="leftButton_1" runat="server" Text="KING" /> <br /> <asp:Button ID="apple" CssClass="button1" OnClick="leftButton_2" runat="server" Text="APPLE" /> </td> <td width="60%" alig ...