How to add files dynamically

Hi;

Is it possible to dynamically add files to the installer rather than hard-coding.
e.g.
StrCpy $0 "abc.xyz"
File $0
I've tried it but getting error. Is there any workaround. The solution given in

One Installer with Different Installation Files Each Time

is not fulfilling my requirement.

Thanks

Can anyone tell me, why the compiler generates error (i.e. File: "$0$1" -> no files found.) for following code.

StrCpy $0 "/testing/"
StrCpy $1 "abc.xyz"
${Package} $0 $1

!macro Package FilePath FileName
File "${FilePath}${FileName}"
!macroend
!define Package "!insertmacro Package "

File is compile time, StrCpy and variables are runtime