Try employing an IF test. For example:
{MERGEFIELD Seat_No} Science: {MERGEFIELD Science}
{MERGEFIELD Seat_No} Maths: {MERGEFIELD Maths}


{MERGEFIELD Seat_No} {IF{MERGEFIELD English}= "#" "Marathi: {MERGEFIELD Marathi}" "English: {MERGEFIELD English}"}

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

how to do it for the following
Say there are three 3 optional papers

O7 O8 O9
Eco # # 10
Pol 12 # #
Psy # 13 #

=IF(AND(J4="#",K4="#"),"Psy",IF(J4="#","Pol","Eco" ))

how to use "AND" in word mail merger.
thank you