codice:
Private Declare Function SetThreadPriority Lib "kernel32" _
    (ByVal hThread As Long, ByVal nPriority As Long) As Long
    
Private Declare Function SetPriorityClass Lib "kernel32" _
    (ByVal hProcess As Long, ByVal dwPriorityClass As Long) As Long
    
Private Declare Function GetThreadPriority Lib "kernel32" _
    (ByVal hThread As Long) As Long
    
Private Declare Function GetPriorityClass Lib "kernel32" _
    (ByVal hProcess As Long) As Long


Private Const THREAD_BASE_PRIORITY_MAX = 2
Private Const THREAD_PRIORITY_NORMAL = 0
Private Const THREAD_BASE_PRIORITY_MIN = -2

Public Enum Priority
    Alta = &H80
    Normale = &H20
    Bassa = &H40
End Enum



Public Function setPriority(ClassePriorità As Priority)
Dim hThread As Long
Dim hProcess As Long

    hThread = GetCurrentThread
    hProcess = GetCurrentProcess
    
    If GetPriorityClass(hProcess) <> ClassePriorità Then
        Select Case ClassePriorità
            Case Is = Alta
                SetThreadPriority hThread, THREAD_BASE_PRIORITY_MAX
            Case Is = Normale
                SetThreadPriority hThread, THREAD_PRIORITY_NORMAL
            Case Is = Bassa
                SetThreadPriority hThread, THREAD_BASE_PRIORITY_MIN
        End Select
        
        SetPriorityClass hProcess, ClassePriorità
    End If

End Function
per chiamarla

codice:
call setpriority(alta)