- 詳くわしいことが分わかり次第しだい、ご連絡れんらくいたします。

kuwashii koto ga wakari shidai, go renraku itashimasu.

As soon as we learn more details, we will get in touch. formal

- 荷物にもつが届とどき次第しだい、連絡れんらくします。

nimotsu ga todoki shidai, renraku shimasu.

As soon as the package arrives, I'll get in touch. neutral