Please please help me create an alert of this perfect indicator

 

I humbbly request the pros, gurus, experts out here to please help make this indicator sound an alert when it crosses the center line which is 15.5. I tried it myself hundred times but it just doesnt want to work when i do it but i guess i am nothing compared to u great experts with perfect knowledge of coding. i hope that u will create an alert of this indicator. i have posted the indicator with screenshot of the crossing where i want the alert to sound i have put an arrow in there. please someone help me in this matter

 

Where is your indicator and its screenshot? I am guessing that you miss to attach it. Please share it again.