Excel Referencing the amount of cells selected by Cell A in Cell B

I have a task that requires me to (in Cell A[Sheet2]) to select a series of cells in column Q in another sheet (Call it Sheet1) and then average that value.

What I want (Cell B[sheet2]) to do is count how many cells in Cell A were selected for this calculation.

I've tried the following with no success=COUNTA(INDIRECT(P4)) where P4 is Cell A and the formula is keyed into Cell B

Any help would be appreciated

Cell A currently has this formula in it

=AVERAGE(AST!P1860,AST!P1863,AST!P1864,AST!P1865,AST!P1866,AST!P1867,AST!P1868,AST!P1869,AST!P1870)

I want Cell B to count the selection of the cells in that forumla and tell me how many there were.