An update:

I now have this functionality working in T-SQL.. bu tI would dearly LOVE to have the expression in the Derived Column do this job.

In T-SQL I am using the following:

select

RefNumber,SUBSTRING(RefNumber, 1, (CHARINDEX('/',[RefNumber],1 )-1)) as Store,

SUBSTRING([RefNumber],(CHARINDEX('/',[RefNumber],1 )+1),(CHARINDEX('/',[RefNumber],4)) - (CHARINDEX('/',[RefNumber],1)+1)) as Till,

SUBSTRING([RefNumber],(CHARINDEX('/',[RefNumber],4 )+1),(CHARINDEX('$',[RefNumber],4)) - (CHARINDEX('/',[RefNumber],4)+1)) as Trans_Num

from imported_data

select

SUBSTRING([RefNumber],(CHARINDEX('/',[RefNumber],1 )+1),(CHARINDEX('/',[RefNumber],3)) - (CHARINDEX('/',[RefNumber],1)+1)) as Trans_Num

from RefTable

which is returning the data in the format I'd like it.

Can anyone give me a pointer?

Paul