iif field contains z the change colour

hello all

i am trying to change the font colour based on an iif statement generally these are easy but ive come across this issue 

=IIf(InStr(Fields!Description.Value, "z*","Red","Black") what im trying to do is this 

if the value contains z then make it red else make it black 

or better still if the value starts with a z then make it red else make it black either solution would be great 

Steve mason