regex - WPF Validation, Regular expressions, repeating entries -

I am validating a textbox in WPF data should be entered in a text box like 2x1500 3X3300 7X3699; The number of entries can be 'n'

I can validate for a single entry [2x1500] and as a regular expression, I will call @ "^ \ d {1,10} X \ D {1,10} $ ". How to make a value, if they put several entries in a text box like I explained earlier [2x1500 3X3300 7X3699]

  @ "^ ((\ d {1,10} X \ d {1,10}) \ s?) + $"