Sending money to someone....conditionally

I'm looking for a website, like PayPal where you can send money where initially the recipient can see it but can't take it out until you give further authorization.

For example. Bob in Dallas needs a service from Mike in Houston. Bob is afraid Mike might not show up, and Mike doesn't want to drive to Dallas for no reason, suspecting Mike doesn't have the money. So Bob sends the money to Mike through this service where Mike can see that the funds are available...but he can't withdraw. When they meet in Dallas, Bob "unlocks" it and Mike proceeds to do the work.
Kind of like POs pretty much, for companies.


For those that use PayPal, it will be like seeing the transfer but not being able to "claim" it until the next step by sender.

Hope that makes sense . Is there a website/service that does something like this?

Thanks