Checkbox Control using Expressions

Hi all,

I'm trying to control the Mask Layer property in the Colorama plugin to always select the current layer. What I've done is created a Checkbox Control effect on the current layer to dictate that Mask Layer is always set to the current layer's index. If the Checkbox Control is set to off, I would like it to select layer "None". Here's what I've come up with, but since I'm new to expressions, it's not working. What am i doing wrong?

if (effect("Checkbox Control")(1)==true){
effect("Colorama")("Mask Layer")=layer(index);
}else{
effect("Colorama")("Mask Layer")=layer(None);}

Thanks in advance for your expertise!