Input box with numbers and string.

I'm trying to do something like this: when the user pressed the button, it will first ask him to put selection 0 text with ok and cancel button. If he presses ok, it will ask agajn but for selection 1 and so on. It will stop when he presses cancel and append the text to the textbox in the format like:

#L0#Input Text#l#L1#Input Text#l

#Lx#text#l

#Lx# is the selection number.
Text is the input string.
#l ends the selection.

So if he puts text and presses ok and then cancel, the appended text will be:

#L0#Text#l

If he puts text and presses ok 4 times and then cancel, it'll be:

#L0#Text#l#L1#Text#l#L2#Text#l#L3#Text#l

Is it possible? If so how. I'm stuck.