Can you code in VBA that a user gets prompted to enter values in one or more shape date elements when they insert a new stencil shape into a diagram?
You also can use Shape Data for this.
About two minutes video
PS Sorry for my terrible speech ;D
No VBA needed, just right-click on the shape and select Define Shape Data.
Create the data items you want here, one of the options for each item is "Ask on drop", so when the shape is dropped on the page a dialog box will open asking for the values.