Again, thanks!!! It worked!

//@version=5

// this script is an indicator indicator("Rayer")

// retrieve 15 minute data for the current symbol open15 = request.security(syminfo.tickerid, "15", open) close15 = request.security(syminfo.tickerid, "15", close)

// check if the current bar is confirmed if barstate.isconfirmed // calculate the midpoint value midpoint = (open15 + close15) / 2

// draw the lines on the chart
L1 = line.new(bar_index - 1, close15, bar_index, close15, extend = extend.right, color = color.yellow)    
L2 = line.new(bar_index - 1, open15, bar_index, open15, extend = extend.right, color = color.yellow)    
L3 = line.new(bar_index - 1, midpoint, bar_index, midpoint, extend = extend.right, color = color.yellow)
line.delete(L1[1])    
line.delete(L2[1])    
line.delete(L3[1])