changing average Query

[joebox8]

hi..
I want a Query to calculate the average of all the text boxes that have non-zero values in them. I have 16 text boxes that could potentially all be filled however i would like to be able to calculate only the average of what has been inputted.
Im sure its fairly simple i just cant think of it.. I hope you know what im asking.. The calculation might be 8 values one time and 16 the next.
My textboxes are named x1...x16.


Any help would be great!

[joebox8]

I reckon its along these lines however this is a mess and doesnt work...

SELECT x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16,
( x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10 +x11 + x12 + x13 + x14 + x15 + x16) As Total,
IIf (x1=0,0,1)+IIf (x2=0,0,1)+IIf(x3=0,0,1)+(x4=0,0,1)+(x5=0,0,1)+(x6 =0,0,1)+(x7=0,0,1)+(x8=0,0,1)+(x9=0,0,1)+(x10=0,0, 1)+(x11=0,0,1)+(x12=0,0,1)+(x13=0,0,1)+(x14=0,0,1) +(x15=0,0,1)+(x16=0,0,1) As Avg,
IIF (Avg=0,0,Total/Avg) as Average)
FROM LAC;