Source Text slider apparition

Hi,

I would like to use a slider to display a text (when the slider value is 0, the source text display nothing, when it is 10, the source text display the 10 first letters etc...). Like the Typewriter animation effect (but I need it with a Source Text expression)

I created a slider named "TextSlicer"

Wrote a text layer

And this expression in Source Text :

try

{

text.sourceText.split("")[Math.round(effect("TextSlicer")("Slider"))] 

}

catch(err)

{text.sourceText }

With this expression, I can display one letter at time.

My goal would be to display N letters, based on the slider value :

text.sourceText.split("")[0] + text.sourceText.split("")[1] + text.sourceText.split("")[2] + text.sourceText.split("")[n] ............

Thanks !