Open Word Work Order Template with excel generated work order #

Hello,

I am working on creating a work order system, and what I'd like to have it do is when I open the Word template (which is my actual work order), it will generate a W/O # from the Master W/O list (my excel spreadsheet). I would like the macro to search the master spreadsheet for the first blank "D" cell row, and use the corresponding "A" cell # as the W/O#. So if "D5" is the next blank row, then the value of "A5" would be the work order number.
I'm attaching the Word and and a sample excel file.
any and all advice is appreciated.