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EXHIBIT 31.2
 CERTIFICATION OF CHIEF FINANCIAL OFFICER OF THE REGISTRANT,
PURSUANT TO 17 CFR 240.13a  15(e) OR 17 CFR 240.15d  15(e)
  1.
    
    I have reviewed this quarterly report on Form 10-Q of Dynamex Inc.;2.
    
    Based on my knowledge, this report does not contain any untrue statements of a material fact
or omit to state a material fact necessary to make the statements made, in light of the
circumstances under which such statements were made, not misleading with respect to the period
covered by this report;3.
    
    Based on my knowledge, the financial statements, and other financial information included in
this report, fairly present in all material respects the financial condition, results of
operations and cash flows of Dynamex Inc. as of, and for, the periods presented in this
report.4.
    
    The registrants other certifying officer and I are responsible for establishing and
maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a  15(e)
and 15d  15(e)) and internal control over financial reporting (as defined in Exchange Act
Rules 13a-15(f) and 15d-15(f) for the registrant and we have:
 a.
    
    Designed such controls and procedures, or caused such disclosure controls and
procedures to be designed under our supervision, to ensure that material information
relating to the registrant, including its consolidated subsidiaries, is made known to
us by others within those entities, particularly during the period in which this
report is being prepared;b.
    
    Designed such internal control over financial reporting, or caused such
internal control over financial reporting to be designed under our supervision to
provide reasonable assurance regarding the reliability of financial reporting and the
preparation of financial statements for external purposes in accordance with generally
accepted accounting principles;c.
    
    Evaluated the effectiveness of the registrants disclosure controls and
procedures and presented in this report our conclusions about the effectiveness of the
disclosure controls and procedures, as of the end of the period covered by this report
based on such evaluation, andd.
    
    Disclosed in this report any change in the registrants internal control over
financial reporting that occurred during the registrants most recent fiscal quarter
that has materially affected, or is reasonably likely to materially affect, the
registrants internal control over financial reporting;
 5.
    
    The registrants other certifying officer and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the registrants auditors and the
audit committee of registrants board of directors;
 a.
    
    All significant deficiencies and material weaknesses in the design or
operation of internal controls which could adversely affect the registrants ability
to record, process, summarize and report financial information; andb.
    
    Any fraud, whether or not material, that involves management or other
employees who have a significant role in the registrants internal controls over
financial reporting.
 Date: March 12, 2007/s/ RAY E. SCHMITZName: Ray E. SchmitzTitle: Vice President and Chief Financial Officer