WDB ACFT ON ILS APCH HAD RAPID COURSE DEV WHICH WAS CAUSED BY ATC CHANGING ILS TO THE RECIPROCAL RWY WHERE ANOTHER ACFT WAS ON APCH.

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AT 3000 FT MSL CLRED TO INTERCEPT RWY 4L LOC ON A 070 DEG HDG. RWY 4L WAS THE ACTIVE RWY. THE LOC FREQ HAD BEEN TUNED AND IDENTED. AS WE APCHED THE COURSE IT APPEARED WE SHOT THROUGH THE COURSE SO A HDG OF 010 DEGS WAS TAKEN TO INTERCEPT. DAY QUESTIONED US AND RETURNED US TO A 070 DEG HDG. THE MXQ VOR WAS TUNED TO XCHK THE ILS AT WHICH POINT WE REALIZED THE ILS WAS GIVING US ERRONEOUS INFO. AT THIS POINT WE PICKED UP THE FIELD VISUALLY AND WERE CLRED FOR THE VISUAL. UPON CONTACTING TWR WE QUESTIONED HIM ABOUT THE LOC AND HE REPLIED HE HAD SWITCHED THE ILS TO RWY 22R TO ACCOMMODATE AN OPPOSITE DIRECTION ACFT AND RETURNED IT TO RWY 4L AFTER HE LANDED. WE WERE GIVEN NO WARNING OF THE XFER BY DAY. SINCE RWY 4L AND RWY 22R UTILIZE THE SAME FREQ; WE RECEIVED NO WARNING FLAGS. WE SIMPLY RECEIVED AN INDICATION OF A COURSE SWING WHICH IS WHAT WE WERE LOOKING FOR BUT IT MOVED RAPIDLY TO THE OPPOSITE SIDE. OUR ATTEMPT TO RE-INTERCEPT ACTUALLY TOOK US FURTHER FROM COURSE. THIS COULD HAVE BEEN A DANGEROUS SIT -- ONE WHICH MAY ARISE AGAIN SINCE IT APPEARS TO BE STANDARD PRACTICE BY TWR TO SWITCH LOCS FROM ONE DIRECTION TO THE OPPOSITE DIRECTION WITHOUT KNOWLEDGE OF APCH CTL.