OptionExplicit
PrivateDeclareFunctionShowWindowLib"user32"(ByValhwndAsLong,ByValnCmdShowAsLong)AsLong

PrivateDeclareFunctionFindWindowLib"user32"Alias"FindWindowA"(ByVallpClassNameAsString,ByVallpWindowNameAsString)AsLong

PrivateDeclareFunctionIsIconicLib"user32"(ByValhwndAsLong)AsLong

PrivateDeclareFunctionSetForegroundWindowLib"user32"(ByValhwndAsLong)AsLong

ConstSW_RESTORE=9

PrivateConstOPEN_APPLICATION=0
PrivateConstSINGLE_INSTANCE_OPEN=1

SubMain()
DimMultiInstResultAsInteger

MultiInstResult=MultiInst

IfMultiInstResult=OPEN_APPLICATIONThen
Form1.Show
ElseIfMultiInstResult=SINGLE_INSTANCE_OPENThen
End
EndIf
EndSub

PrivateFunctionMultiInst()AsInteger

DimhwndFoundAsLong
DimstrWindowName

strWindowName=App.Title
App.Title="temptitle"
hwndFound=FindWindow(vbNullString,strWindowName)

IfhwndFoundThen
MultiInst=SINGLE_INSTANCE_OPEN
MsgBox"Ainstanceoftheapplicationisalreadyopen."&vbCrLf&vbCrLf&"Onlyoneopeninstanceallowed.",vbOKOnlyvbExclamation,"AppName"