Formatting Text Areas

I'm having some problems with formatting text areas. I'm trying to get the program to color certain words that appear in the text area for a programming text editor. Here's the code.

Global Mainwin=CreateWindow("Mainwin",0,100,640,480,Desktop(),3)

Global SaveButt=CreateButton("Save",0,0,25,25,Mainwin,1)
SetGadgetLayout(SaveButt,1,0,1,0)
Global OpenButt=CreateButton("Open",25,0,25,25,Mainwin,1)
SetGadgetLayout(OpenButt,1,0,1,0)

Global MainArea=CreateTextArea(0,23,631,423,Mainwin,0)
SetTextAreaColor(MainArea,243,243,243,True)
tmpfont=LoadFont("Arial",14)
SetTextAreaFont MainArea,tmpfont
SetGadgetLayout(MainArea,1,1,1,1)

HotKeyEvent(28,0,$FFFF)

Repeat
	event=0
	event=WaitEvent()
	Select event
	Case $803
		Exit
	Case $FFFF
		AddTabs(MainArea)
	Case $401
		Select EventSource()
		Case MainArea
			;Stop
			LockTextArea mainarea
			FormatTextAreaText(mainarea,1,1,1,0,0)
			UnlockTextArea mainarea
			ColorText(MainArea," Xor ; And ; Or ; Not ",255,0,0)
		End Select
	Default
	End Select
Forever

HotKeyEvent(28,0,0)

Function colortext(TextArea,ColorString$,colorr,colorg,colorb)
	Strng$=TextAreaText$(textarea)
	While Instr(ColorString,";",LastFindExt+1)
		Strng$=TextAreaText$(textarea)
		NextHighLight$=Mid$(ColorString,LastFindExt+1,Instr(ColorString,";",LastFindExt+1)+LastFindExt-1)
		LastFindInt=0
		While Instr(Lower$(strng),Lower$(NextHighLight),LastFindInt+1)
			Strng$=TextAreaText$(textarea)
			LockTextArea mainarea
			FormatTextAreaText(TextArea,ColorR,ColorG,ColorB,0,Instr(Lower$(strng),Lower$(NextHighLight),LastFindInt+1)-1,Len(NextHighLight),1)
			UnlockTextArea mainarea
			LastFindInt=Instr(Strng,nexthighlight,LastFindInt+1)
		Wend
		LastFindExt=Instr(ColorString,";",LastFindExt+1)
	Wend
End Function

Function AddTabs(TextArea)
	linenum=TextAreaCursor(TextArea,2)
	lineabove$=TextAreaText(TextArea,linenum-1,linenum,2)
	I=1
	While (Mid$(lineabove,I,1) = "	") And (I < Len(lineabove))
		I=I+1
	Wend
	For J=1 To I-1
		ret$=ret$+"	"
	Next
	SetTextAreaText(TextArea,ret,TextAreaCursor(MainArea,1),0,1)
	For J=1 To I-1
		keypress(39,0,0,0)
		keypress(39,0,2,0)
	Next		
End Function

P.S. you'll need this userlib in order to run the program http://www.blitzbasic.com/codearcs/codearcs.php?code=1227.