Function XML_Replace 

Pop $R7 ; section 
Pop $R4 ; string to replace 
Pop $R3 ; string to search for 
Pop $R9 ; file name to patch 

IfFileExists $R9 0 mmmmm_please_stop 

GetTempFileName $R8 

FileOpen $R1 $R9 "r" 
FileOpen $R2 $R8 "w" 

loop_one: ; goes next the section tag 

FileRead $R1 $R5 

IfErrors mmmmm_please_stop 

FileWrite $R2 $R5 

Push $R5 
Push $R7 
Call StrStr 
Pop $R6 
StrCmp $R6 "" loop_one 0 

FileWrite $R2 "$R3$R4" 
FileWriteByte $R2 "13" 
FileWriteByte $R2 "10" 

loop_two: 

FileRead $R1 $R5 

IfErrors done 

Push $R5 ; read string 
Push $R3 ; searched string 
Call StrStr ; we check if string searched is inside 
Pop $R6 
StrCmp $R6 "" 0 lets_turn 
FileWrite $R2 $R5 

lets_turn: 

Goto loop_two 

done: 
ClearErrors 

FileClose $R2 
FileClose $R1 

Delete $R9 

Rename $R8 $R9 

mmmmm_please_stop: 

FunctionEnd