Timer Not Working

Hi

I am trying to call a function from a timer using the following code:

var mTimer;
function testTimer()
{
mTimer = app.setInterval( "runTimer()", 1000 );
}

function runTimer()
{
app.clearInterval(mTimer);
app.alert("timer run");
}

The function runTimer() simply doesn't run.

The only way I can get the timer to work is with a line like this:

mTimer = app.setInterval( "app.alert('test')", 1000 );

However, calling a function doesn't work.  The code is in a global module.  It doesn't work with anything I try, such as:

mTimer = app.setInterval( "Global.runTimer()", 1000 );

I am using a Dynamic XML form in Designer 9 (trial version).

Many thanks

Geoff Olding