You say the contents of A1 is text, I am sure there are many who would like to know how you sum text if it is text I suppose you could sum the characters, but as there is no numeric value there is not much to sum.
Because relative addressing has been used , if you enter the formula =Calc in B1 , it will refer to the contents of A1 and evaluate the expression entered in cell A1.
If you enter an expression in cell D2 , and you want it evaluated , enter the formula =Calc in cell E2.
The formula will always evaluate the contents of the cell which is in the same row , and one column to the left of the cell where it is entered.