Call Fuction From Query Code

i have a sample function


Function GetPercent(n As Integer) As Integer
Select Case n


Case 1: GetPercent = 100
Case 2: GetPercent = 50
Case 3: GetPercent = 0
End Select
End Function


I have a table like this

a | b | c | d | e | f | percent
----------------------------------------
1 | 2 | 1 | 3 | 3 | 1
3 | 1 | 3 | 2 | 1 | 3
1 | 2 | 1 | 1 | 2 | 1
2 | 2 | 3 | 3 | 1 | 2
1 | 1 | 1 | 2 | 2 | 3

1 = 100
2 = 50
3 = 0

for example the first row

1 | 2 | 1 | 3 | 3 | 1
(100+50+100+0+0+100) / 6

I think if I can call function from query than I write like it:

strSQL = "update table set percent = " & GetPercent(a) + GetPercent(b)
CurrentDb.Execute (strSQL)


but sure that I got an error because its not find the a and b

how can I do it?
good day!