I need to add a numeric mask to a toolstrip textbox

Question

I have a menu item Open that had a submenu item of a textbox to open a file. The file format for the client is xx-xxxxx. In a separate search function, I have a maskedtextbox with the appropriate mask. The client has asked that I apply this mask to the Menu->Open option.

 

Menu option to change:

 

 

Example of search function: