showing message box if the result of texbox doesn't match with the range then clear texbox

Hi;

1- As my attached file, i want to show messaage box in case of the result of texbox1 (ID+Candidate) doesn't match in the range ( C column ).
2- I wonder if ther is a way to create a dynamic combobox2 depends on combobox1.

So many thanks in advence.