There are two parts to a checkbox control (the text label and the checkbox itself), and six ways to arrange them, as shown here (from the TSTCBZ sample program in EXLIB).
The checkboxes in the upper group were created with these AUI_CONTROL calls:
xcall AUI, AUI_CONTROL, OPCODE, ID(1), "Left Text; Left Justify", MBST_ENABLE, MBF_CHKBOX + MBF_LFTEXT + MBF_LFJUST, CMD$, CB1, STATUS, 2, 2, 2, 24, 67, -2, 0, 0, "", "", GRPID1
xcall AUI, AUI_CONTROL, OPCODE, ID(2), "Left Text; Right Justify", MBST_ENABLE, MBF_CHKBOX + MBF_LFTEXT + MBF_RTJUST, CMD$, CB2, STATUS, 3, 2, 3, 24, 67, -2, 0, 0, "", "", GRPID1
xcall AUI, AUI_CONTROL, OPCODE, ID(3), "Right Text; Left Justify", MBST_ENABLE, MBF_CHKBOX + MBF_LFJUST, CMD$, CB3, STATUS, 5, 2, 5, 24, 67, -2, 0, 0, "", "", GRPID1
xcall AUI, AUI_CONTROL, OPCODE, ID(4), "Right Text; Right Justify", MBST_ENABLE, MBF_CHKBOX + MBF_RTJUST, CMD$, CB4, STATUS, 6, 2, 6, 24, 67, -2, 0, 0, "", "", GRPID1
xcall AUI, AUI_CONTROL, OPCODE, ID(5), "Left Text; Center Justify", MBST_ENABLE, MBF_CHKBOX + MBF_LFTEXT, CMD$, CB5, STATUS, 8, 2, 8, 24, 67, -2, 0, 0, "", "", GRPID1
xcall AUI, AUI_CONTROL, OPCODE, ID(6), "Right Text; Center Justify", MBST_ENABLE, MBF_CHKBOX, CMD$, CB6, STATUS, 9, 2, 9, 24, 67, -2, 0, 0, "", "", GRPID1
The checkboxes in the lower group were created with INFLD, which only supports four of the six possible alignments:
xcall INFLD, 2, 2, 23, 0, "||c", CB$(1), INXCTL, GRPID2+1, 2, EXITCODE, 0, 0, -1, -1, -1, "Left Text; Left Justify"
xcall INFLD, 3, 2, 23, 0, "||c|J", CB$(2), INXCTL, GRPID2+1, 2, EXITCODE, 0, 0, -1, -1, -1, "Left Text; Right Justify"
xcall INFLD, 5, 2, 23, 0, "||cR", CB$(1), INXCTL, GRPID2+1, 2, EXITCODE, 0, 0, -1, -1, -1, "Right Text; Left Justify"
xcall INFLD, 6, 2, 23, 0, "||cR|J", CB$(2), INXCTL, GRPID2+1, 2, EXITCODE, 0, 0, -1, -1, -1, "Right Text; Right Justify"
TYPE code legend: ||c is for checkbox; R reverses the normal alignment (putting the checkbox on the left and the text on the right), and |J right justifies the text. (|J is the same as setting SBR=INFLDCBRJ but has the advantage of being easy to change from one field to the next.)
INFLD uses the SETDEF parameter for specifying the text associated with checkboxes.