LoTROInterface - ListBox number/string error (Help!)

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ListBox number/string error (Help!) [SOLVED]

Heres the scenerio. Im making a Listbox for user input. The input range is 0-9999 and everything works according to plan with this until the next step.
Im placing an if-then-else-end statement in to check that no other characters/letters are used, for the listbox to be wiped clean and a message to the user that they inputted illegal data, but im getting 'attempt to compare number with nil' error.

Is there anything i can do to either allow the lua to ignore the error and carryon with the if-then-else-end statement or allow it to not do an error at all?

heres the code i have at the moment-

Code:

    ImageAmountInput:SetWantsKeyEvents( true );

    

    ImageAmountInput.KeyDown = function( sender, args )

        

        if args.Action == 162 then

            OpWindow:Activate();

            ImageAmountInput:SetSelection( 1, 4 );

            IAI = ImageAmountInput:GetText();

            IAI = tonumber( IAI );



            if  IAI >= 0 and IAI <= 9999 then -- ERROR produced here if non-numerical characters are used in user input box.

                ImageAmountInput:SetSelection( 0, 0 );

            else

                ImageAmountInput:SetText( "" );

                print ( "You entered an illegal entry" );

            end



        end



    end

You could always use a function to strip out the non-numeric characters and then check if it equals that which was entered.

Lua string tutorial at; http://lua-users.org/wiki/StringLibraryTutorial

Hehe, ive just added an if-then-end before it to check if its not tonumber( IAI ) :)

I guess the small break from staring at code gave me a little brain boost.

p.s. thanks for your fast response btw MrJackdaw :D

edit-

Code:

ImageAmountInput:SetWantsKeyEvents( true );

    ImageAmountInput.KeyDown = function( sender, args )

        

        if args.Action == 162 then

            OpWindow:Activate();

            ImageAmountInput:SetSelection(1, 4);

            IAI = ImageAmountInput:GetText();

            IAI = tonumber( IAI );

            if not tonumber( IAI ) then -- <--- Fixes everything

                ImageAmountInput:SetText( "" );

                print ( "You entered an illegal entry" );

            elseif  IAI >= 0 and IAI <= 9999 then -- ERROR produced here if string characters used in user input box. Need to figure out a way to ignore erroring.

                ImageAmountInput:SetSelection(0,0);

            end

        end

    end