OnClick increase number in field on form

[DCV0204]

I have a field named "BoxNumber" and my first number is "M00001".



I would like for the field to auto populate with this number until I click a button named "newbox"; then
I would like the new number "M00002" to auto populate until I click the button again for the next box.
Each time I click the button it should increase the box number by 1.

Is this possible?
thanks,
Lisa

[ranman256]

on click,

dim iNum as integer
dim vLast ,vNewNum

vLast = mid(BOXNUMBER,2)
iNum = vLast + 1
vNewNum = "M" & format(iNum,"00000")

    'new record
DoCmd.GoToRecord , , acNewRec
BOXNUMBER = vNewNum