Derived Column Transformation Expression

Hi.

I am using the following expression to check if the first charcter of a string is not the letter "E" and if it is, strip it off by selecting the remainder of the string:

SUBSTRING([Derv.comno],1,1) == "E" ? SUBSTRING([Derv.comno],2,10) : [Derv.comno]

This is ok in 99.9% of cases, but ideally I would like to be able to check, and alter the string if the first charcter is anything but numeric

I had something like this in mind:

SUBSTRING([Derv.comno],1,1) != ("1","2","3") ? SUBSTRING([Derv.comno],2,10) : [Derv.comno] 

but the syntax is incorrect.

Could you tell me if what I am attempting is actually possible, and if so, point me in the right direction regarding the syntax!

Thanks