Writing formulas

I have created a wookbook that has many worksheets.
The sheets are basically activity logs for different
individuals. I am then using other sheets in this workbook
to compile the individual sheets for a composite report.
On the idividual worksheets I have a column that gives the
type of case it is. The columns that follow are activities
for that month, with the cell under that activity having an
"X" placed in it it that activity was done. What I am trying
to do is write a formula that looks at the case type column
to see what type it is, ie "PR", "PA", "ISC", then if it
is a "PR" to look over in the activity column and if there
is an "X" to count it. I want the total number of "X"'s, for that
case type and activity, for the entire sheet.

Can you help?

Thanking you in advance,
Sean-Patrick