How to pass relative path to strings in Self-Extraction Directive file?

Question

I’m using IExpress to create a self-extracting / self-installing package (.EXE) and a Self-Extraction Directive file (.SED). When moving the files from a test environment to a production one, I’ve noticed that the strings TargetName (target path and filename of the package) and SourceFiles0 (folder of the packaged files) were hardcoded, and so the creation of a new package failed because no folder/files were found in the “old” path.

[Version] 
Class=IEXPRESS 
SEDVersion=3 
[Options] 
PackagePurpose=InstallApp 
ShowInstallProgramWindow=1 
HideExtractAnimation=1 
UseLongFileName=1 
InsideCompressed=0 
CAB_FixedSize=0 
CAB_ResvCodeSigning=0 
RebootMode=N 
InstallPrompt=%InstallPrompt% 
DisplayLicense=%DisplayLicense% 
FinishMessage=%FinishMessage% 
TargetName=%TargetName% 
FriendlyName=%FriendlyName% 
AppLaunched=%AppLaunched% 
PostInstallCmd=%PostInstallCmd% 
AdminQuietInstCmd=%AdminQuietInstCmd% 
UserQuietInstCmd=%UserQuietInstCmd% 
SourceFiles=SourceFiles 
[Strings] 
InstallPrompt= 
DisplayLicense= 
FinishMessage= 
TargetName=C:\Test\MyPackage.exe 
FriendlyName= MyPackage 
AppLaunched= MyPackage.cmd 
PostInstallCmd=<None> 
AdminQuietInstCmd= 
UserQuietInstCmd= 
FILE0="MyPackage.cmd" 
FILE1=" MyPackage.ps1" 
[SourceFiles] 
SourceFiles0=C:\Test\MyChildFolder\ 
[SourceFiles0] 
%FILE0%= 
%FILE1%= 

I’ve tried writing just the filename for TargetName or child folder for SourceFiles0, but I’ve got an error message. The same goes for “.\” or ”%~dp0” or ”$(srcdir)\” (without the double quotes) I’ve tried using IExpress GUI wizard and command-line tool.

Does anyone know how to pass a path relative to the .sed file itself to those strings?