after the then , press enter and type let and then $(tTriggerKO).... also close this if statement with endif (inside the loop)
but if Nom_Ctrl has more then 1 value in the data set this statement will only change 1 time because after the first iteration the variable is already 2 .
if you don't want that you can move this let statement to the end of the script and do something like this
if $(vTest) = 1 then;
let vTest = 2;
endif;