Importing Data From External Data Source Using in Formulas

I have imported data from a .mdb file into a worksheet, and by using vlookup i am using the data in another sheet in the same book. The value returned by vlookup is presented accordingly lets say i.e. Param1, but when i use that value in a formula for example =SUM(param1, param2), the formula doesnt work as the Param1 is not accounted in the total sum.

But on the other hand if i go to the worksheet where the data is imported and i double click the cell for some sort of formatting, then the data becomes usable in the other worksheet and subsequently the formula too.

Need some help regarding this.