ms word - Mergeseq disappears in my mail merge code -

i'm new mail merge documents. i'm trying simple thing, explained in source:

http://support.microsoft.com/kb/294686/en-us

just trying out basic code:

{if {mergeseq} = "1" "true" "false"} 

but if switch "preview results" on , off, code becomes

{if = "1" "true" "false"} 

what's going on? can tell syntax should have been correct. why did word kick mergeseq away?

{ mergeseq } generates sequence number when merge. when you're previewing, doesn't generate result (or if prefer, generates empty result). alt-f9 once or twice should reveal field code again.

so behaviour in fact "expected", if rather confusing, particularly since { mergerec } behaves differently.

(as aside, preview guide happen when merge. it's best test actual merge need).