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You will need to issue a subpoena for a third party (or non-party) deposition.
This article discusses this practice and the civil procedure rules involved: http://www.zelle.com/news-publications-266.html
And here is a sample subpoena (it is for Harris County, you will need a notice specific for your county, please note, it must be issued by the Court Clerk): http://www.hcdistrictclerk.com/Common/Forms/pdf/CIVCP02_Witness_Deposition_Subpoena_Subpoena_Duces_Tecum.pdf
Use of deposition transcripts at trial (in lieu of live testimony by the witness) is a strategy call, and you run a risk of compromising your testimony by relying on deposition transcripts in place of witness testimony.
However, Texas does permit deposition transcripts to be introduced at trial.
I would recommend reviewing this article: http://www.agtriallaw.com/papers/talkingheads.pdf which discusses strategy considerations and the rules associated with depositions (both taking, defending, and using them).
The information on trial practice begins on page 28.