用vb计算表达式s=-x+2x^2/3!-4x^4/5!+6x^8/7!-…,x属于[1,2],要求计算精度为第n项的值

dim i as integer
dim s as double
dim dx as double
dim x as double
inputbox x
dx=-x
s=dx
i=1
while dx>0.00001
dx=(-1)^(i+1)* 2i*x^(2i) / (2i+1)
s=s+dx
i=i+1
loop