can someone help me with the if/else script

I have an input form field called howmany

and a form field call Result

Lets say the form field gets a 2

I put the following code in the custom calculation property of the Result field

var tst=this.getField("howmany");

if(tst.value>1)

event.value=tst.value*10;

else

event.value=tst.value*5;

I cant seem to get any kind of if /else block to work

If somebody could shed some light on what I need to do it would be greatly appreciated.

I cant seem to find any resources that will explain the syntax for Adobe Acrobat Javascript

I'm using Acrobat Pro DC