I need to make an update query that

[Mabjro]

I need to make an update query that will work like find and replace. For example, if there were a field with the following value "whzt" and I wanted to search for the "z" and make it an "a", how would I do it using an update query. I have scaled this example down a great deal. I need to work with multiple records at a time with multiple criterea, that is why it would be great if an update query would work.
Thank you for your help,
Mabjro

 

[Mabjro]

Oops, I posted this twice. I will check both for responses. Thanks