SequentialAnimation, how to reduce the gap.

[mrdebug]

Hi everybody. I have implemented the "SequentialAnimation on y {" to obtain a floating object from Y to Y+ 30. How can I reduce the gap (30 to zero) dinamically?

@ SequentialAnimation on y {
loops: Animation.Infinite;
NumberAnimation {
from: y- floatgap / 2;
duration: floattime
easing.type: Easing.InOutQuad;
to: y+ floatgap / 2;
}
NumberAnimation {
from: y+ floatgap / 2;
duration: floattime
easing.type: Easing.InOutQuad;
to: y- floatgap / 2;
}

}@