Hopefully you will like the following solution:
Open userform, enter data in userform, click on "Find Record".
A sheet will be made visible with all the records with the same ClientLN or Coach.
On this sheet (Search results) there are 2 buttons: Update and Cancel.
Cancel: Remove search results, hide sheet and return to "Input master" sheet.
Update: First select the cell or row that you wish to update (this is also what the button tells you) and click the "Update" button.
A message box appears if you didn't select a valid record.
A message box appears displaying the selected record and the record initially entered in the userform.
This is to confirm the update action. So either click on Cancel to stay on sheet and possibly choose another record to replace or click on OK. This will update (basically replace) the record on the "Input Master" sheet.
The only way to leave the "Search results" sheet is to use the buttons.
Note that the "Update" button is fully called:
Select row and hit this button to update record in Input Master sheet.
Note that the "Cancel" button is fully called:
Cancel search action.
Finally note that the "Update Record" button on the userform lost it's intended purpose and can be removed if you choose to work with this solution.
Here is your file:
Although it is not exactly what you asked, I think that it works pretty nicely.