Subtracting a comma separated string from another in Excel [closed]

If I have A1= 1,2,3,4,5,6,7,8,9

A2=2,6,9

My desired result should be in cell A3 After substation (A1-A2) =1,3,4,5,7,8

while it was very easy when A2=2,3,4 (serially) via substitute function.