Find maximum of 2 dates in different DGs in extract xml in BI Publisher Excel template

Summary

Find maximum of 2 dates in different DGs in extract xml in BI Publisher Excel template

Content

Hi experts, I have an excel template ( from a benefits extract) in BI Publisher &  I need to find the maximum between

<CI_Ori_Enrol_Date>2023-09-01T00:00:00.000Z</CI_Ori_Enrol_Date>
<A_Ori_Enrol_Date>2020-10-01T00:00:00.000Z</A_Ori_Enrol_Date>

<xsl:variable name="a" select="Emp_Enrol_Acc_T_Rec/Emp_Enrol_Acc_DG/Emp_Enrol_Acc_Rec/A_Ori_Enrol_Date"/>
<xsl:variable name="b" select="(Emp_Enrol_CI_T_Rec/Emp_Enrol_CI_DG/Emp_Enrol_CI_Rec/CI_Ori_Enrol_Date)[1]"/>