Not sure if I understood your request correctly, but this is how I use point filters:
In my partial .MNS I modify the shift+right-click pop-up menu and type X or Y hotkeys to get the point filter, the menu macro just returns the X or Y value of the selected point. I had this in R12 way before object tracking. The first CAD system I used, AES, had this as a standard point entry feature. I believe I got the menu code from old softdesk menus.
The key concept is:
starting a line from point A
if you want the .X value of point B
type .Y or .YZ, then NON (no snaps) then @ (to use values of last point A)
AutoCAD then wants the X value, so select B
Dan
my entire POP menu for reference - custom point filters in Red
***MENUGROUP=A+S
***POP0
**SNAP
[&Object Snap Cursor Menu]
ID_ZoomPrevi [Zoom &Previous]'_zoom _p
ID_PanPick [&Pan Pick]'_-pan
[--]
ID_TrackingOld [Rubberband Trac&king]_tk
ID_Tracking [Temporary track point]_tt
ID_From [&From]_from
ID_MnPointFi [->Point Fi<ers]
ID_PointFilx [.X].X
ID_PointFily [.Y].Y
ID_PointFilz [.Z].Z
[--]
ID_PointFixy [.XY].XY
ID_PointFixz [.XZ].XZ
ID_PointFiyz [<-.YZ].YZ
[--]
ID_OsnapEndp [&Endpoint]_endp
ID_OsnapMidp [&Midpoint]_mid
ID_OsnapInte [&Intersection]_int
ID_OsnapAppa [&Apparent Intersect]_appint
ID_OsnapExte [Extension]_ext
[--]
ID_OsnapCent [&Center]_cen
ID_OsnapQuad [&Quadrant]_qua
ID_OsnapTang [&Tangent]_tan
[--]
ID_OsnapPerp [& Perpendicular]_per
ID_OsnapPara [Para&llel]_par
ID_OsnapNode [No&de]_nod
ID_OsnapInse [In&sert]_ins
ID_OsnapNear [Nea&rest]_nea
ID_OsnapNone [&None]_non
[--]
//Trap for pline command only taking 2d points
[color=red] [Hold &X]$M=$(if,$(or,$(eq,$(substr,$(getvar,cmdnames),1,5),PLINE),$(eq,$(substr,$(getvar,cmdnames),1,5),PEDIT)),.Y,.YZ) non @
[Hold &Y]$M=$(if,$(or,$(eq,$(substr,$(getvar,cmdnames),1,5),PLINE),$(eq,$(substr,$(getvar,cmdnames),1,5),PEDIT)),.X,.XZ) non @
[Hold &Z].XY non @
[/color] [--]
[&1 Midpt of 2 pts]non (midpt)
[&2 Last Point (@)]non @
[&0 World Origin]non *0,0,0
[Dwg Insertion &Base Pt]non (getvar "insbase")
[Snap Base]non (getvar "snapbase")
[--]
ID_Osnap [&Osnap Settings...]'_+dsettings 2
in the matching .MNL file to load the custom POPs
;;; ;;Replace the right mouse button pop-up menu
(menucmd "A1=A+S.AUX1")
(menucmd "A2=A+S.AUX2")
(menucmd "A3=A+S.AUX3")
(menucmd "A4=A+S.AUX4")