I filed a lien on a homeowner and they are withholding funds and I would like to know if it is possible to file a motion of discovery before our lien court date
If the property is the owner's homestead (meaning that the owner owns the property and lives there) then your contract with the owner would have to satisfy the requirements of Texas Property Code sections 53.254, et seq., which requires specified homestead lien warnings, signing by husband and wife, and recordation in the county property records.
You really should retain a construction attorney to review and evaluate your legal position based on the contract and pertinent documents. The right to be entitled to file a mechanic's lien is set out in Texas Property Code Chapter 53, and you really need to make sure that if you file a lien, you have properly and appropriately done so.
Filing an invalid lien could subject you to liability under the Texas Fraudulent Lien Act, and you could be liable for statutory damages of $10,000, or actual damages, whichever is greater, plus attorney's fees. Facing such a claim would add insult to injury.
You mention a court date, but do not indicate that you filed suit to enforce your mechanic's lien, and to secure a judgment on the debt that the owner owes. You really need to retain a construction attorney to evaluate your situation and to provide advice.
Good luck.