Could you tie your validation script to the "submit" button or whatever you are using for the user to "save" changes...
For Each Control in Userform1.Controls
If Control.Type Like "TextBox" Then
That syntax may not be exact but I have done similiar data validation at the end of a userform by cycling through the controls by either Control.Name or Control.Type then performing data validation that way.
If invalid data is entered you can change properties of the text box to indicate to the user, such as making background color red, or font red, etc..