I'm going to try this.
PROCEDURE myMin
LPARAMETERS f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, ;
f12, f13, f14, f15, f16, f17, f18, f19, f20
LOCAL lcFld as String, lnMin as Number
lnCrazyLargeNumber = 9999999
lnMin = lnCrazyLargeNumber
FOR i = 1 TO PCOUNT()
lcFld = "f" + ALLTRIM(STR(i))
IF TYPE(lcFld) == "N"
IF &lcFld < lnMin
lnMin = &lcFld
ENDIF
ENDIF
ENDFOR
IF lnMin == lnCrazyLargeNumber
RETURN .null.
ELSE
RETURN lnMin
ENDIF
ENDPROC and then call it like this (and include cast)
SELECT *, CAST(mymin(f1, f2, f3, ...) AS N(10,4)) as mymin FROM mytable
