Display blank cell when formula returns non-numeric value. Please HELP

Disclaimer: I know enough excel to be dangerous, now I need help with "compound formulas"

The below formula is what I am working with:

=IF(MasterTable!BV2="","",IF(MasterTable!BW2="",TEXT(MasterTable!BV2,"(###) ###-####"),TEXT(MasterTable!BV2,"(###) ###-####"&" x"&MasterTable!BW2)))

This formula pulls and concatenates phone number cell and extension cell from master table into a "reorg" worksheet. As long as the master fields contain numeric values, then everything displays properly. However, as soon as a "genius" types text characters in a field it displays as "#VALUE!". what I need is if ALPHA characters exist in these phone number fields, to display blank in the destination cell.

I feel sheepish now!. Thank you for your help!!