Numbers in formulas keep changing

Hi. I have set up a spreadsheet with a lot of formulas in it. I find that sometimes on opening the spreadsheet, the figures in some of the formulas have changed. For example:
=COUNTIF(Pre_implementation!$P$2:$P$200,"Apple")+COUNTIF(Implementation!$P$2:$P$200,"Apple")+COUNTIF(Completed!$P$2:$P$200,"Apple") becomes
=COUNTIF(Pre_implementation!$P$3:$P$201,"Apple")+COUNTIF(Implementation!$P$4:$P$202,"Apple")+COUNTIF(Completed!$P$2:$P$200,"Apple")

Is this to do with me deleting lines from the pages the formula is counting from? And how can I set it up so that the figures don't change (ie. I always want it to count from rows 2 to 200). Thanks alot.

maybe

=COUNTIF(INDIRECT("'"&A1&"Pre_implementation!$P$2:$P$200"),"Apple")+COUNTIF(INDIRECT("'"&A1&"Pre_implementation!$P$2:$P$200"),"Apple")+COUNTIF(INDIRECT("'"&A1&"Pre_implementation!$P$2:$P$200"),"Apple")