Hi Muhtashim,
If I am understanding you correctly you want to create a condition and code the SPL code yourself?
It should work but, no guarantee and is not supported so if it doesn't work you would have to look at a different solution. The table itself is splmac.
You would use one of ours as an example where the type is COND. The spl code goes in fragment and give it a valid persid with a matching id. Try and use it and see if it works but, there is no guarantee it will.