Counting columns in a dynamic range

[seleseped]

Hello,
I have an attendance sheet where students' names are in column A, attendance percentage (calculated using data from columns C and beyond) in column B, and the dates of classes are in columns C and beyond. A new column is filled with each class held where 'true' indicates that the student was present in class and 'false' if not. To calculate the attendance percentage, I need to count the number of 'true' values in columns C and beyond. I would like help with an Excel formula (not VBA) which counts the number of filled columns to determine the denominator of the percentage. I know that something like:

=COUNTIF(3:3,"TRUE")

will not work since cells A3 and B3 do not include attendance data and give a circular reasoning error since my calculated result is in B3. I need a formula which starts at C3 then identifies the last filled column in row 3. I could use a far-right cell reference such as:
=COUNTIF(C3:ZZ3,"TRUE") but that is not elegant programming technique and I need to learn!

Thanks to you in advance for your time and expertise!

 

[Aladin Akyurek]

What kind of data do you have in C3 on - text or number?

 

[seleseped]

What kind of data do you have in C3 on - text or number?

The data are text ('true' or 'false').
Thank you.

 

[Aladin Akyurek]

The data are text ('true' or 'false').
Thank you.

Does this help?

c3:index(c3:zz3,match(rept("z",255),c3:zz3))

 

[seleseped]

Does this help?

c3:index(c3:zz3,match(rept("z",255),c3:zz3))

I don't think so. I gave the ZZ3 as an example. In reality, the number of columns changes. For example, one week the columns may go from C to G, then the next week (after 5 more classes) the columns will go from C to L. I need a formula which will count the number of columns as they expand to the right over time.

Thank you.

 

[Aladin Akyurek]

I don't think so. I gave the ZZ3 as an example. In reality, the number of columns changes. For example, one week the columns may go from C to G, then the next week (after 5 more classes) the columns will go from C to L. I need a formula which will count the number of columns as they expand to the right over time.

Thank you.

c3:index(c3:zz3,match(rept("z",255),c3:xfd3))

match(rept("z",255),c3:xfd3)

provided that all those true's are text, not a logical value, as you claimed.