vba to auto increase an ID number

What I want to do is have a textbox or other form control look at a data list and then assign a new ID number automatically.

For example: the form as selected on the main menu sheet will look at range B:B and then assign the next sequential number CR0002 when a new record is created.

When the user clicks the New ECR command button on the main menu sheet the ID Number textbox will display the next available number in the sequence without user input.

I've looked at some rather convoluted methods for this, but I'm betting there is a quite simple method available .

As always
Thank you for all input.

Thank you both for the help, works great.