EXCEL VBA - Make a msgbox warning if cell is matches content of another cell -

i'm school principal , i'm trying make scheduling managment app in excel.

i have 1 sheet each class , 1 sheet each teacher.

all sheets same , have important information on same coordinates.

for now, i've been able make classes timetables copy on teacher's , works charm. make students timetables , automatically makes teacher's.

now have bit of problem.

if assign teacher to, let's monday @ 8.30 1 class , then, mistake assign same teacher class overlaps , carries on first class teacher. last week same teacher assign 2 classes @ same time.

so question this:

is there way make (on cell change) vba script checks if cell b29 has same value on other sheets, regardless of sheet's possition , name?

ex:

i assign teacher class 1 - monday 8.30 teacher name , date/hour cell b29, class cell d5 , sheet name.

if assign, in class, same teacher b29 if display msgbox saying "there overlap".

what have trouble every year classes , teachers change , relative position of sheets change due year of course , number of courses/classes,

thanks!

i think code this: copy code sheet(code):

private sub worksheet_change(byval target range)      if not intersect(target, range("b29")) nothing         if selection.cells.count = 1             result = gettime(range("b29").value)         end if     end if  end sub 

copy code module1

function gettime(timeadd date)      each ws in worksheets         if ws.name <> activesheet.name             if ws.range("b29").value = timeadd                 result = true                 exit             end if         end if     next      if result = true msgbox "there overlap."  end function 

hope help