Inno UninstallRun How To get global variable by executing - inno-setup

Question

My target is to read a registry entry at [UninstallRun].
The issue is, if Inno Setup is running in an install process the Function GetRegistryVar() is called here ? It should be called when the UnInstall process is running. If I start the UnInstall process the Function GetRegistryVar() will not called here ? Only the CurUninstallStepChanged() and PGetRegistryVal(). So I can't receive my global variable gStrPrnName ?
[UninstallRun]
Filename: "{#dInst64bitDir}\{#dUnInstDrvExeName}"; Parameters: "-f {code:GetGlobalRegistryVar}"; WorkingDir: "{#dInst64bitDir}"; Flags: runhidden runascurrentuser;
[Code]
var
gStrPrnName: string;
function GetGlobalRegistryVar(Value: string): string;
begin
Result := gStrPrnName;
end;
procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
begin
case CurUninstallStep of
usUninstall:
begin
// ...insert code to perform pre-uninstall tasks here...
PGetRegistryVal(gStrPrnName);
end;
usPostUninstall:
begin
// ...insert code to perform post-uninstall tasks here...
end;
end;
end;
function PGetRegistryVal(Value: String): String;
var
strPrnName: string;
i: Integer;
begin
for i:=0 to 2 do
begin
if RegQueryStringValue(HKLM, 'SOFTWARE\Microsoft\Windows NT\CurrentVersion\GetDevice_1', 'Name', strPrnName) then
Result := strPrnName;
if RegQueryStringValue(HKLM, 'SOFTWARE\Microsoft\Windows NT\CurrentVersion\GetDevice_2', 'Name', strPrnName) then
Result := strPrnName;
...
end;
end;
Has somebody a solution for this issue ?
Thanks