help with my base converter

[Nizzem]

This is my poorly made prog:

code:

% The "GUI.CreateTextFieldFull" program import GUI View.Set ("graphics:200;100,nobuttonbar") var TextField : int  % The Text Field IDs. var answer,answer3,answer5 : string var answer2,answer4,answer6 : int  var addressLabel := GUI.CreateLabelFull (45, 40, "Base_?:", 0, 0,        GUI.RIGHT, 0)   procedure AddressEntered (text : string)     GUI.SetSelection (TextField, 0, 0)     GUI.Quit end AddressEntered  proc base10 cls     GUI.SetBackgroundColor (gray) GUI.Refresh     var convert := GUI.CreateButton (52, 5, 100, "Convert", GUI.Quit)     TextField := GUI.CreateTextFieldFull (50, 40, 100, "",         AddressEntered, GUI.INDENT, 0, 0)   GUI.SetLabel (addressLabel, "Base_10")           loop         exit when GUI.ProcessEvent     end loop     GUI.Dispose (convert)     answer := GUI.GetText (TextField)     colorback (gray)     Text.Locate (maxrow - 1, 1)     put "Base_2: ", intstr (strint (answer), 0, 2)     put "Base_16: ", intstr (strint (answer), 0, 16)     end base10 proc base16     GUI.SetBackgroundColor (gray) GUI.Refresh     var convert := GUI.CreateButton (52, 5, 100, "Convert", GUI.Quit)     TextField := GUI.CreateTextFieldFull (50, 40, 100, "",         AddressEntered, GUI.INDENT, 0, 0)   GUI.SetLabel (addressLabel, "Base_16")    loop         exit when GUI.ProcessEvent     end loop GUI.Dispose (addressLabel)         answer3 := GUI.GetText (TextField)     colorback (gray)     Text.Locate (maxrow - 1, 1)     answer4 := strint (answer3, 16)     put "Base_10: ", answer4     put "Base_2: ", intstr (answer4, 0, 2)     end base16 proc base2 cls GUI.SetBackgroundColor (gray) GUI.Refresh     var convert := GUI.CreateButton (52, 5, 100, "Convert", GUI.Quit)     TextField := GUI.CreateTextFieldFull (50, 40, 100, "",         AddressEntered, GUI.INDENT, 0, 0)    GUI.SetLabel (addressLabel, "Base_2")       loop         exit when GUI.ProcessEvent     end loop         answer5 := GUI.GetText (TextField)     colorback (gray)     Text.Locate (maxrow - 1, 1)     answer6 := strint (answer5,2)     put "Base_10: ", answer6     put "Base_16: ", intstr (answer6,0,16) end base2 GUI.Refresh var binary : int := GUI.CreateButtonFull (1, 75, 0, "Binary",             base2, 0, '^D', true) var decimal : int := GUI.CreateButtonFull (72, 75, 0, "Decimal",             base10, 0, '^D', true) var hex : int := GUI.CreateButtonFull (150, 75, 0, "Hex",             base16, 0, '^D', true)   loop         exit when GUI.ProcessEvent     end loop

Right now I want to add an input checker to it. So that when entering a binary number if the number isn't 1 or 0 it would highlight the number and give you the opportunity to change it. As far as I understand the code for that should look something like this:

code:

procedure CheckInput (s : string)             for i : 1 .. length (s)                 if (s (i) < '0' or '1' < s (i)) and s (i) not= ' ' then                     GUI.SetSelection (TextField, i, i + 1)                     return                 end if             end for             GUI.Quit         end CheckInput

But I am unable to successfully intergrade it into my program. If anyone could help me it would be appreciated.