How to asynchronously execute a function? - vb.net

Question

I am working on a vb.net application and I am struggling to get this function to run in parallel. This is a legacy application, I was told that it uses an event-based asynchronous pattern, but I do not exactly understand what that means for this problem.
There is a for loop that runs a function serially, but I would like to run it in parallel.
Public Function Execute() As Boolean
Dim ret As Boolean = True
' If output files are not specified, then they will be generated based on the study name
If CancelExecution Then Return CancelCleanUp()
If ValidateInputFiles() Then
If CancelExecution Then Return CancelCleanUp()
Select Case _Name
Case "Main Single"
' This is the for loop I would like to run in parallel
For Each cc As IOFile In _CCards
If ValidateOutputFiles(cc.FileName) Then
ret = RunModel(cc)
If CancelExecution Then Return CancelCleanUp()
Else
ret = False
End If
Next
' The other Cases are irrelevant
End Select
Else
ret = False
End If
Return ret
End Function
Private Function RunModel(cCard As IOFile) As Boolean
Dim uFile As String
Dim ret As Boolean = True
If CancelExecution Then Return CancelCleanUp()
' create the uconfiguration file
If _RunNumber > 0 Then
uFile = MakeUFile(cCard, _InputFiles, _OutputFiles, _RunNumber)
Else
uFile = MakeUFile(cCard, _InputFiles, _OutputFiles)
End If
' Input: was not part of the vb 6 IInputModel class, but added in this version
' Main: delete files mainmodel is about to create (even the optional files) (calls CleanUpSingleRun)
ret = KillIOFiles(_OutputFiles)
' execute the application
If File.Exists(uFile) Then
Dim arg As String = """" & uFile & """"
If _Name = "Main Single Sensitivity" Then
' 7/27/2105 add an argument for either single or production run - this is a single run module
arg = arg & " SINGLE" & " " & "NOVIZ"
End If
ret = RunApplication(arg)
Else
Return False
End If
'execute? did it terminate properly?
' kill the ufile
Try
File.Delete(uFile)
Dim cleanupFiles = Directory.GetFiles(_SensitivityFolder).Where(Function(e) e.Contains(".spw") Or Path.GetFileName(e).StartsWith("SIMU")).ToList()
For Each fileToDelete As String In cleanupFiles
File.Delete(fileToDelete)
Next
' clean up temp combined files
If CombinedFile <> "" Then System.IO.File.Delete(CombinedFile)
Catch ex As Exception
End Try
ret = VerifyOutputFiles(cCard.FileName)
Return ret
End Function
Any help is very much appreciated, thank you for taking the time to read my post.