Run-time error '1011'. The argument value is not valid. when running macros in ms project 2010

Hi All

Through the Wizard, I import an excel document into Ms Project 2010 and then I run a small macro which works fine up to the point I want to delete a row which is not needed. An error comes up: Run-time error '1011'. The argument value is not valid. Do you know how to fix it please?

Thank you in advance