Logix5000 - Tag inside a tag

I've written a ladder program, on PLC5 that inserts a tag within a tag. I've tried this in logix5000 and I keep getting an error. How should I write this in Lx5000?

Here's the PLC5 code:

ADD Source A T4:15.ACC Source B N300:[N300:0] Dest N300:[N300:0] 

Thanks

in RSLogix5000 index (indirect address) must be tag, not array element.

Thanks!