Solved. Thanks to an old post from @Lindon , thanks!
inline function onbtn_GET_SAMPLE_LENGTHControl(component, value)
{
if (value)
{
local selection = SP_1.createSelection(".*");
local sampleStart = selection[0].get(SP_1.SampleStart);
local sampleEnd = selection[0].get(SP_1.SampleEnd);
Console.print("Sample Start: " + sampleStart + ", Sample End: " + sampleEnd);
}
};
Content.getComponent("btn_GET_SAMPLE_LENGTH").setControlCallback(onbtn_GET_SAMPLE_LENGTHControl);