Sum return values of a function inside a loop

[AIisKing 0]

Hello AutoIT community, 
 

Without getting into too much details about the script. I have general question - what is the best way to sum return values of function inside a loop? I have limited programming skills and I don't seem to get it working.

An example of what the script should do: Script opens excel files from a selected folder and cleans the each file. CleanExcelFiles function returns integer $iCount which counts the amount of rows deleted in an excel file. 
 

Example()

Func Example()

Local $sFileSelectFolder = FileSelectFolder("", "")

$aFileList = _FileListToArray($sFileSelectFolder, "*.xls")

Local $iResult = 0
For $i = 1 To $aFileList[0]
    $sFile = $sFileSelectFolder & "\" & $aFileList[$i]
    
    OpenExcelFiles($sFile)

    $iResult = CleanExcelFiles()
    
Next

MsgBox("", "", "Total of "& $iResult& "actions were performed in all excels.")
EndFunc

Please advise a solution to sum all $iResults and return this total value after the script has finished cleaning all the excels.

 

[Nine 1,181]

$iResult += CleanExcelFiles()

That will sum up all results

[AIisKing 0]

@Nine I was thinking about +=, but for some reason I was getting syntax error. 

What can be the case that I get syntax error?

The CleanExcelFiles return integer $iCount.

Edited January 17 by AIisKing