I am using the list box, choose more, I don't know how to show his value in the design of Access query, use VBA spell list box to choose the value of the cycle after a string

"A", "b", "c"

Now want to put the string as a condition to the query conditions of the design, but can not query, because he put it in, should become the "' a ', 'b', 'c'"

I think in the conditions used in (" a ", "b", "c") but is now a string variable parameters, how could he converted into parameter to use?