When using a formula, there have been a number of occasions when I wanted to pass a value to an agent. To pass values to formula agents, simply run some formula that sets a profile field and in the agent read the profile field data back in as the variable.
testval := @Prompt([OKCANCELEDIT];"TEST";"Enter the value to be passed to the agent";"test");
value := @GetProfileField("TEST";"VAL");
@Prompt([OK];"TEST";"The value passed to the agent was " + value + ".")