Calling a specific station without interference?

There has been a small number of times that I've needed to repeatedly call a specific DX station (XT2 for example) while others call me.  After two calls to the specific station, my QSO/TX# area is taken over by one of the callers.  This is aggravating to say the least.  How do I retain the QSO/TX# information of the original DX station I wish to work?

Thanks

Harry @ KH6CW