Repeat Region Relation Help Needed

[Cygnus A]

I need to override some titles of parts that are released in a drawing BOM and I can't figure out the relation needed to do so. I tried creating a new parameter as shown below:

desc1 = " "

if exists("asm_mbr_partnumber")
     desc1 = &asm.mbr.nomenclature&asm.mbr.title1&asm.mbr.title2&asm.mbr.title3
endif

if exists("asm_mbr_partnumber")
     if asm_mbr_partnumber == "1234"
        desc1 = "NEW DESCRIPTION"
     endif
endif

It seems to be failing due to the multiple strings added together. What is the correct syntax for this?