It is exactly what the topic is all about
hmm! but you asked how the client can ask the wallet provider to block/freeze your money. maybe I am just confused
anyways, this is what I had in mind:
OP_CHECKLOCKTIMEVERIFY https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki
when it is used, it makes a transaction unspendable until the time is reached. effectively it freezes the funds for a specific amount of time. but it freezes a transaction output.
there may be wallets with this option, but the only tool that I know of is this: https://coinb.in/#newTimeLocked