[Gehrman]

Thank you Cesar
After_Install works as well as ISExec.

[Record1]
Type=After_Install
Source={cmd}
Output=/c start "" "https://fileforums.com/"
Disk=1
Component=1

[Record2]
Type=FreeArc_Original
Source={src}\Data1a-01.bin
Output={app}\
Disk=1
Size=2.521.712 bytes

[Record3]
Type=After_Install
Source={cmd}
Output=/c start /w "" "{src}\Arc.exe" x -kb -ba- -dp"{app}" "{src}\TEST.arc"
Disk=1

[Record4]
Type=After_Install
Source={src}\Arc.exe
Output=x -o+ -kb -ba- -dp"{app}" "{src}\TEST.arc"
Disk=1