First you need to start a new drawing file.
Then pick on the logo to pull down what you see below.
hover over the "drawing utilities" and then pick on "drawing properties"
Create whatever kind of name you want for a custom property; in mine I am creating one called Client.
now, you have done this in the drawing; you will also want to duplicate this in the titleblock drawing file.
that way when you go to insert it into a drawing it, but we will cover more of the titleblock setup soon.
Once you have done this you are done with this new drawing file for a minute.
Open up your titleblock file, and go through and create the custom property as you did in the other drawing file. Be sure that the property name is identical in both files.
Now that you have created the custom property, you can set up an attribute to reference this new custom property that you set up. Here is how we are going to do that.
Double pick on the attribute that you are wanting to change or create a new attribute; in this case I have a multi-line attribute that is easy to change. Next, we will pick on the button to the right of the default box to open up the text editor
Select the line of text that you are wanting to have linked to the custom property, and then pick on the add field button on the far left of the "text formatting" bar.
The below dialog will show, and as you can see in the field names column you can see the custom property that I created, so we will select it and on the right column we will select uppercase so that no matter how i type it in it will always come in as uppercase letters.
Now, once you do that hit the "ok" buttons until you are out of the attribute editing and then save your titleblock.
With this being done; go into the other drawing file and change to the layout1 tab, and insert the titleblock.
Once you have done this save this drawing file as a template that way everything will automatically be setup for you each time you start a new drawing.
This can be done with lots of custom properties in the title blocks. I have a title block that probably contains 10-15 linked properties.
And anytime that you change a property value; all you have to do is either regenall or do the updatefield command.