"Use a melee attack" reads to me as "you roll as for a melee attack..." - thus, you can't make a missile attack or likewise.
The text is very specific in the SRD for Disarm, Trip and Grapple: Action Type Varies; substitutes for a melee attack.
Check table 8-4 on page 128 of the PHB:
Standard Actions
Strike a weapon (attack)
Action Type Varies
Disarm(*)
Grapple(*)
Trip an opponent(*)
*: These attack forms substitute for a melee attack, not an action. As melee attacks, they can be used once in an attack or charge action, one or more times in a full attack action, or even as an attack of opportunity.
###
The PHB is extremely confusing about actions, breaking them into
Attack Actions
Magic Actions
Partial Actions
Miscellaneous Actions
When instead the relevant terms are
Free Actions
Move-Equivalent Actions
Standard Actions
Full-Round Actions
Action Type Varies
Cheers!