flat assembler - WritePrivateProfileStringA

I was writing a program the other day where i wanted to store some information in INI files. When looking through the MSDN, i found there was no WritePrivateProfileInt function for writing integers to ini files.

So i wrote a procedure which calls wsprintf to convert the number to a string, then writes the string to the ini file with WritePrivateProfilestring. As far as i can see, im passing all the corect paramaters to the functions, however WritePrivateProfileString is failing every time, with last error being ERROR_NOACCESS. I searched for a few hours to try and find why however could not find a reason. Does anyone know why this could be?

I write a simple test case which reproduces the problem. The following code tries to write 0x100 (256) to Test.ini and (on my system at least) fails as described above.

Code:

FORMAT PE GUI 4.0
Entry _Main

Include '%Include%\Win32A.inc'

Section '.code' Code Readable Executable
        
    _Main:
  
    ;       Get full path name of INI file
      push NULL
   push szFilename
     push MAX_PATH
       push szIniFile
      call [GetFullPathName]
      
    ;        call my WritePrivateProfileInt function
    push szFilename
     push 0x100
  push szKeyname
      push szSectionName
  call WritePrivateProfileInt
 
    invoke ExitProcess, 0
       
    proc WritePrivateProfileInt, szApplication, szKey, Value, szFilename
                
            ;       allocate 11 bytes of data for the string to go in on the stack
              push edi                ;       a decimal integer in string form 
           sub esp, 11             ;       will only take a maximum of 10 bytes
                mov edi, esp    ;       extra byte for null terminator
              
            ;       reset the buffer to NULL bytes
              xor al, al
          mov ecx, 11     
            push edi
            rep stosb
           pop edi
             
            ;       get string equivalent of value...
           push [Value]
                push .FormatString
          push edi
            call [wsprintf]
             
            ;       write string to ini file.
           push [szFilename]
           push edi
            push [szKey]
                push [szApplication]
                call [WritePrivateProfileString]
            
            ;       ollydebug should show last error to
         ;       be ERROR_NOACCESS here if your getting
              ;       the same problem as me.
             
            ;       restore the stack
           add esp, 11
         pop edi
             
            ret
         
    ;       the string used by wsprintf to generate the string format of the number
     .FormatString DB '%i', 0
  endp
        
    
Section '.data' Data Readable Writeable
       
    Data Import
         
            library kernel32,                               'kernel32.dll',\
                         user32,                                 'user32.dll'
                              
            import kernel32,\
                  GetFullPathName,                        'GetFullPathNameA',\
                     WritePrivateProfileString,      'WritePrivateProfileStringA',\
                   ExitProcess,                            'ExitProcess'
                     
            import user32,\
                    wsprintf,                                       'wsprintfA'
                       
    End Data
    
    szIniFile DB 'Test.ini', 0
        szSectionName DB 'TestSection', 0
 szKeyname DB 'TestKey', 0
 
    szFilename RB MAX_PATH

any help is appreciated. Thank you.