Merge PDF using pdftk after saving

Hello I try to merge pdf files with pdftk with vbs scrit after saving.

WshShell.Run PathToPdftk & " “”" & tfname & “”"" & " " & “”"" & DriverRules & “”"" & " cat output " & “”"" & tfname & “”"" ,0,True

DriverRules contains path to pdf witch should be merged with new created pdf.

Script always end with errors: that tfname does not exist. Adding stamps and watermark works fine but I cannot find how add to the end another pdf from external path.

Thanks for any help