Tim,

I used the windows api and implemented it as a class.
I hope this is what you need.

Bob Lee

#DEFINE ERROR_ALREADY_EXISTS 183
LOCAL oMutex, lcFormCaption
lcFormCaption = "SE New GoldMine Record Ver 8.00"
oMutex = CREATEOBJECT("Mutex", lcFormCaption)

IF oMutex.nMutexError # ERROR_ALREADY_EXISTS
* The instance doesn't exist
DO form newrec7 NAME ofrmnewrec linked
READ events
ELSE
* It does exist so display the
* original instance before terminating
oMutex.DisplayInstance()
ENDIF
oMutex = .NULL.

DEFINE CLASS Mutex AS CUSTOM
cFormCaption = ""
hMutex = 0
nMutexError = 0
PROCEDURE Init
LPARAMETER pcFormCaption

DECLARE INTEGER CreateMutex IN Win32API;
STRING @lpMutexAttributes,;
STRING bInitialOwner,;
STRING @lpName

DECLARE INTEGER GetLastError IN Win32API

LOCAL lcInitOwner, lcName, lcFormCaption

* So that the Mutex name is different
* from the caption.

lcFormCaption = pcFormCaption
lcName = CHRTRAN(pcFormCaption, SPACE(1), "")

* Simulate a BOOL type equaling TRUE.

lcInitOwner = CHR(1)

WITH THIS
.cFormCaption = lcFormCaption
.hMutex = CreateMutex(0, lcInitOwner, @lcName)
.nMutexError = GetLastError()
ENDWITH
RETURN
ENDPROC

PROCEDURE DisplayInstance
* This procedure is used to display
* an instance of the application.

DECLARE INTEGER FindWindow IN Win32API ;
STRING @lpClassName, STRING @lpWindowName

DECLARE SHORT IsIconic IN Win32API ;
INTEGER hWnd

DECLARE INTEGER ShowWindow IN Win32API ;
INTEGER hWnd, INTEGER nCmdShow

DECLARE SHORT BringWindowToTop IN Win32API ;
INTEGER hWnd

LOCAL lcFormCaption, lnhWnd, llIcon

lcFormCaption = THIS.cFormCaption
lnhWnd = FindWindow(0, @lcFormCaption)
IF NOT EMPTY(lnhWnd)
* Determine if the Application
* is minimized (an icon).
llIcon = (IsIconic(lnhWnd) # 0)
IF llIcon
* It is an icon, so restore it
= ShowWindow(lnhWnd, 9)
ENDIF
* Make sure it is active.
= BringWindowToTop(lnhWnd)
ELSE
* This handles applications with
* dynamic title text bars.
= MESSAGEBOX("You already have an instance" +;
" of this application running." + CHR(13) +;
CHR(13) + "Please check your task bar", ;
64, "Only one instance allowed.")
ENDIF
RETURN
ENDPROC

PROCEDURE Destroy
DECLARE INTEGER WaitForSingleObject IN Win32API ;
INTEGER hObject, INTEGER dwTimeOut

DECLARE SHORT ReleaseMutex IN Win32API ;
INTEGER hMutex

DECLARE SHORT CloseHandle IN Win32API ;
INTEGER hObject

LOCAL lnResult
IF THIS.hMutex # 0
lnResult = WaitForSingleObject(THIS.hMutex, 50)
* 258 = STATUS_TIMEOUT
IF lnResult # 258
lnResult = ReleaseMutex(THIS.hMutex)
* 1 equals boolean true
IF lnResult = 1
lnResult = CloseHandle(THIS.hMutex)
ENDIF
ENDIF
ENDIF

CLEAR DLLS
RETURN
ENDPROC

ENDDEFINE