You need something like this...
for( i = 0; i < BarCount; i++ )
{
if( Buy[i] ) PlotText( "Buy@" + C[ i ], i-3,low[i]-10, colorDarkBlue, colorSkyblue );
AlertIf(Buy, "SOUND H:\\AMIBROKER\\Sound\\ding.WAV", "Audio Alert", 1);
//if( Cover[i] ) PlotText( "Cover@" + O[ i ], i-3, Low[i]-10...