Excel Solver Error Message

Error messages really need to be formulated with care. I am already confused my code does not work and I would like to see a message that clearly states what is wrong and what I should do to remedy the situation.

A counter example is here:

Two Excel Solver bugs in two lines!! More info on the first one: http://yetanothermathprogrammingconsultant.blogspot.com/2014/04/how-do-they-make-bug-like-this.html.

Just want to make a few quick plots:

Update: fixed by coding the number as a string in the variant. An alternative fix is shown here. Both are not obvious (to me).