Limit text inputs

[EAATC]

I am trying to create a sign up sheet that has timeslots throughout the day. There are 46 available slots however I can only have 25 people sign up per day. Is there a way to create some formula to prevent a 26th person from signing up?

Times are in column A (6-51) text is in B,C, D for day 1: E, F, G for day 2: H, I, J for day 3.

	a	b	c	d	e	f	g	h	I	j
4
5		Title	Last	First	Title	Last	First	Title	Last	First
6	8:30
7	8:40
8	8:50
9	9:00
10	9:10
11	9:20
12	9:30
13	9:40

<tbody>
</tbody>

I cannot have it as a macro. I appreciate any assistance.

 

[etaf]

so 8:30 till 16:00 is the time

you can use data validation

As everyone should enter a last name
column C
then in C you could use a
data validation
custom
and use the formula

=counta($C$6:$C$51)<27

 

[FDibbins]

I was thinking the same thing, except adjust the $ a bit, so it can be copied over for the other days
=counta(C$6:C$51)<26

 

[etaf]

good point FDibbins
and the value , as 26 cannot be added , rather than 26 people , which i have used < 27 rather than the correct < 26
thanks

 

[FDibbins]

OP said no more than 25, that's why I used < 26

 

[etaf]

yes i noticed that and for some reason when I saw

to prevent a 26th person from signing up?

i read as 26 people , rather than the correct 25

 

[EAATC]

so 8:30 till 16:00 is the time

you can use data validation

As everyone should enter a last name
column C
then in C you could use a
data validation
custom
and use the formula

=counta($C$6:$C$51)<27

This worked perfectly. thanks for the prompt assistance. I did use the <26 as later suggested.