How to make checkboxes explicit

[maciek4]

I have 4 checkboxes and I can check all 4 of them, but my goal is to make them explicit. If I check for example A and then decide to change my mind and select B then A will be unselected, but I dont know how to do suck a thing. :bemused:

<td bgCOLOR="#E0E0E0" class="tah11" align=left>
<INPUT TYPE="checkbox" NAME="progress[A]" value="work" <? echo isset($progress['A']) ? 'checked' : ''; ?>>&nbsp;A - du¿y<br>
<INPUT TYPE="checkbox" NAME="progress[B]" value="like" <? echo isset($progress['B']) ? 'checked' : ''; ?>>&nbsp;B<br>
<INPUT TYPE="checkbox" NAME="progress[C]" value="exam" <? echo isset($progress['C']) ? 'checked' : ''; ?>>&nbsp;C<br>
<INPUT TYPE="checkbox" NAME="progress[D]" value="exam" <? echo isset($progress['D']) ? 'checked' : ''; ?>>&nbsp;D - ma³y<br>

</td>

[Weedpacket]

Guessing from your second sentence I think you mean "exclusive", not "explicit". For that behaviour, use radio buttons.