How to select an option or type in a value in the same field
I have a PHP page which updates a MySQL table containing volunteer information - one row for each volunteer. Each volunteer has a field called "assignedactivity", the default value is "Unassigned". Administrators can update the volunteer record to assign a volunteer to an activity by selecting a radio button. This works fine and is shown below.

Now, my users would like to be able to also select an additional radio button - labelled "Other" and then type in an Assigned activity. I have no idea how to do this, if someone could point me in the right direction I would really appreciate it.
Below is the current working code for this field
<table>
<tr>
<td><input type="radio" name="assignedactivity" value="Aircraft Ops/Parking" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Aircraft Ops/Parking"))) {echo "checked=\"checked\"";} ?> />
Aircraft Ops/Parking</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Vehicle Parking" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Vehicle Parking"))) {echo "checked=\"checked\"";} ?> />
Vehicle Parking</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Security" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Security"))) {echo "checked=\"checked\"";} ?> />
Security</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Hospitality" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Hospitality"))) {echo "checked=\"checked\"";} ?> />
Hospitality</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Ramp Patrol" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Ramp Patrol"))) {echo "checked=\"checked\"";} ?> />
Ramp Patrol</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Marketing" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Marketing"))) {echo "checked=\"checked\"";} ?> />
Marketing</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="EAA Booth" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"EAA Booth"))) {echo "checked=\"checked\"";} ?> />
EAA Booth</td>
</tr>
<tr>
<td><input type="radio" name="assignedactivity" value="Unassigned" <?php if (!(strcmp(htmlentities($row_rsVolunteer['assignedactivity'], ENT_COMPAT, 'utf-8'),"Unassigned"))) {echo "checked=\"checked\"";} ?> />
Unassigned</td>
</tr>
</table>
Thanks so much for any advice you may have.
Tony
