The IItemDestroyedBlock function can be added to an Item and will run whenever you try to break a block with the assiciated Item.

It might be required for you to import the package if you encounter any issues, so better be safe than sorry and add the import.
import mods.contenttweaker.IItemDestroyedBlock;

The IItemDestroyedBlock is a function with the following parameters:

• IMutableItemStack stack → The item.
• IWorld world → The world this takes place in
• ICTBlockState blockState → The state of the block that is being mined.
• IBlockPos pos → Where does this take place?
• IEntityLivingBase entity → Who/What mines the block?

The Function needs to return a boolean, that is true if the blockBreaking process is successfull, and false if it ain't.