Just one install should work fine. There are probably hundereds of different ways to do this. One way is to have three different text files or data tables, and pass to escal.php which you want for each calendar.
For example:
Calling code would be something like (simplified)
<table>
<tr>
<td> <?php $name_sel=1; include("escal.php"); ?> </td>
<td> <?php $name_sel=2; include("escal.php"); ?> </td>
<td> <?php $name_sel=3; include("escal.php"); ?> </td>
</tr>
</table>
in escal.php add
switch ($name_sel) {
case 1:
$textFile="file1.txt";
$sqlTable="table1";
break;
case 2:
$textFile="file2.txt";
$sqlTable="table2";
break;
case 3:
$textFile="file3.txt";
$sqlTable="table3";
break;
}
You may have to experiment a bit, but this is a general approach.
tomB