Try this as line 7:

IF ema1[X] Crosses Over ema2[X] Then

Can you explain exactly what are the two conditions to be detected and in which order?

It’s an inner feature of the iteration FOR…NEXT, the counter is first incremented, then the iteration ends when that number is greater than the one betweeen TO and DO. You can ALWAYS subtract 1, unless it is exited with BREAK, as in this case the iteration is exited BEFORE the the counter is incremented. To accomplish that you need to use a variable to be assigned 1 when the counter needs to be drecremented and 0 when it does not (not tested):

Lma= (Average[20](close))
Sma= (average[10](close))
Offset = 10 * pipsize
a= 0
DecValue = 1
// (｡♥‿♥｡) Block Start
IF Sma > Lma Then
For variable= 0 to 15 do
//a=a+1
IF (Sma[variable] > Lma[variable]) then
a=a+1
ENDIF
// a=a+(Sma[variable] > Lma[variable])
 
IF Sma[variable] Crosses Over Lma[variable] Then
BarIndCrosseOver = Barindex[variable]
DecValue = 0
Break
ENDIF
Next
ENDIF
// Block End (｡♥‿♥｡)
 
// (｡♥‿♥｡) Block Start
//condition1= a=variable  //this will assign condition1 a logical value (shoulf be always 1)
condition1= max(0,a-DecValue)
// Block End (｡♥‿♥｡)
 
// (｡♥‿♥｡) Block Start
// Drawing
IF condition1 Then
BACKGROUNDCOLOR (0, 155, 10, 25)
ENDIF
IF condition1 AND NOT condition1[1] Then
DRAWELLIPSE(BarIndCrosseOver-1,LOW[variable]-Offset,BarIndCrosseOver+1,HIGH[variable]+Offset)coloured(255,10,10)
DRAWTEXT("V = #a#", BarIndCrosseOver, Low - Offset)
ENDIF
// Block End (｡♥‿♥｡)
 
Return Lma as "Long SMA", Sma as "Short SMA"