Macro to Communicate Between Excel Drop List and Word Mail Merge

[KCRoyals83513]

I have written this Macro to generate an already linked Mail Merged Doc by simply pushing a Form Control button in Excel:

Sub OpenMailMergeDoc()
Dim wrdApp As Object
Dim wrdDoc As Object
Set wrdApp = CreateObject("Word.Application")
wrdApp.Visible = True
Set wrdDoc = wrdApp.Documents.Open("Z:\file path")

End Sub

Currently, it fills the first row of data by default.

I now need to write another Macro that will read the drop down list that indicates which row of data the user wishes want to fill in the Mail Merge and have it populate that specific row.

Sorry this is a very specific request and I don't even know where to start.

Any help would be greatly appreciated!