I think you mean "hex edits". "ROM map" just refers to the layout of the ROM, not changes made to it.
Anyway, you would either have to:
Rewrite the effect using UberASM, if possible (may not be, depending on what you're doing)
Write an actual patch that hijacks where the hex edit would normally take effect, and then decide whether to use the original code/value or your modified code/value based on the current level number.
Either option would require learning ASM first, as there's no single answer to this question. If you'd like to learn it, I'd recommend starting with this tutorial
Professional frame-by-frame time wizard. YouTube
- SMW Glitch List
- SMW Randomizer