Audio File Player Parameter Issue

used this script in a rackspace with 2 variations:

var PLAYHEAD : Widget
    lblVariationName : Widget
    AFP : PluginBlock

On Variation(oldVariation : integer, newVariation : integer)


SetWidgetLabel(lblVariationName, GetVariationName(newVariation))

if GetVariationName(newVariation) == "Raindrops" then
    SetParameter(AFP, 9, 1.0)
elsif GetVariationName(newVariation) == "Kuhlau Sonatina" then    
    SetParameter(AFP, 10, 1.0)

I understand why after load of the gig the on Variation is not called.
But when it is loaded and the 2nd variation is switched the SetParameter(AFP, 10, 1.0)
has not effect.
If have to switch up to the 1st variation and down again, and then it is working.

As a workaround is used the on Activate Event to switch the 1st variation automatically and then
all is fine.

Do I miss something?