Not natively in Filemaker. There might be a plug in for this if you search around.
Alternatively, you can set a script to run differently depending on whether a modifier key such as Control or Shift is held down.
Your first line of your script would look like this:
If [Get ( ActiveModifierKeys ) = 1 /* Shift key is down */]
# do the things you want to happen when the user holds down shift key
# do the things you want to happen when user just clicks the field, If you just want the user to be able to edit the field, use Go To Field to place the cursor in the field
You can then select the field in layout mode and use Button setup... to specify that this script be performed when the field is clicked.