Figuring Out the Check Digit

function getCheckDigit(x)
	dim a,b,c,a2,a3
	a=""
	b = ""
	c = ""
	a2 = ""
	a3 = ""
	dim upcARR(10)
		for i = 0 to 10
			upcARR(i) = cint(mid(x,i+1,1))
		next

	a = upcARR(0)+upcARR(2)+upcARR(4)+upcARR(6)+upcARR(8)+upcARR(10)
	a2 = a*3
	a3 = upcARR(1)+upcARR(3)+upcARR(5)+upcARR(7)+upcARR(9)
	b = a2+a3
	c = 300-b
	getCheckDigit = (cstr(x) & cstr(right(c,1)))
end function