You could use Bitcoin Script.

// Main script

OP_OVER OP_HASH160 OP_EQUALVERIFY OP_DEPTH 0 OP_GREATERTHAN

OP_IF

OP_VERIFY

OP_ELSE

OP_RETURN

OP_ENDIF

//

OP_CAT OP_HASH256

OP_SWAP OP_CHECKSIG

OP_VERIFY

OP_BOOLAND

//

// Example condition: check if the event content contains a specific string

OP_SWAP OP_SUBSTR OP_NIP OP_EQUALVERIFY

//

// Example: Unlock the UTXO by sending the funds to a specific address

OP_DUP OP_HASH160 OP_EQUALVERIFY OP_CHECKSIG