From http://www.w3schools.com (Copyright Refsnes Data)

WMLScript prompt() Function

The prompt() function displays a message and waits for an input. The second parameter is a default input, that will be returned if the user does not enter a value. This function returns the user input or the default value.

Syntax

n = Dialogs.prompt(message, defaultinput)

Part	Description
n	The string returned from the function
message	A string containing the message (question)
defaultinput	A string containing the default input (answer)

Example

var a = Dialogs.prompt("Enter a number:","3");

Result

a = "5" (if the user entered the value 5)
a = "3" (if the user did not enter a value)

Complete WMLScript Dialogs Library