Reference formula 'Text' within another cell in Excel

I would like to insert text from a cell into a formula... For example: using the formula: =LOOKUP(A1,'Sheet2'!B2:B10, 'Sheet2'!D2:D10) I would like to change 'Sheet2' to some other reference (i.e. Sheet3) - this reference label is contained within another cell within the main spreadsheet. Is there a way to do this? Thanks in advance for any help.