Sure. Here are the steps.
1.) Go to "Table", "Repeat Region", "Relations", then select the region in the table.
2.) Expand the "Local Parameters" section of the window.
3.) Create a new parameter to hold the changing value. Let's call it "NAME" (String)
4.) Make sure "ASM_MBR_NAME" "ASM_MBR_PTC_WM_REVISION" are already listed as parameters. If not, add either manually add them (type doesn't matter) or go back out and temporarily add columns with the parameters (this will add them to the parameters list in the relations.)
5.) Add the following relations to the relations section at the top.
IF SEARCH(asm_mbr_name,"X1") > 0
NAME = asm_mbr_name
ELSE
NAME = asm_mbr_name+asm_mbr_ptc_wm_revision
ENDIF
6.) Exit the relations editor.
7.) Change the repeat region parameter in the table cell that currently reads &asm_mbr_name to instead read &rpt.rel.NAME. This may be simpler by right clicking on the cell and choosing "Report Parameter", "rpt..", "rel.", "User Defined", and then type "NAME".