special query/filter

I have a db group by user ID numbers. In this db I have two fields.
transaction and fund. A user can have more then one transaction what i want
to do is ONLY display if the user put money into the fund AND took out money.

for example
-----------

trans fund
f a
f a
t b
t b
t c
t c


so here the user is not putting in and taking out from the same fund. so none
get displayed but if i added

f c

i would want to display all transactions dealing wit that fund.

if anyone could help i would really appreciate it, i really dont have a clue


thanks
-Jon