Absolutely.
The "mod" function tells you the REMAINDER
after two numbers are divided.
In the case you've completed,
you take the column  number, say 15..
divide it by two.
It goes into 15 seven times, leaving (1) left over.
since 1 does not equal 0, then the
If statement: if(# mod 2 = 0) is false.
For every 18 columns/rows,
simply use if(Target.column mod 18 = 0) the
This would then be true for column 18, 36, 54, 72, etc.