You could use the following expression to display the amount abovementionned, assuming the Excel field name containing the amount is 'Test':

LEFT(TRIM([Test]),LEN(TRIM([Test]))-6) & IF(LEN(TRIM([Test]))>6," ","") & RIGHT(REPLACE(TRIM([Test]),".",","),6)
The expression instructs PSM to:

1. Display the leftmost part of the amount, minus the last 6 characters
2. Display a space as the thousand separator only if the amount string has more than 6 characters
3. Display the 6 rightmost characters of the amount, also replacing the dot by the comma in the process.

Note: This expression doesn't handle all cases: it doesn't add a millon separator, and doesn't take negative amounts into account.

Hope this helps!

NB. There might still be solutions to try, like saving your Excel file with different export settings, such as using a comma instead of a dot as the decimal separator. To learn more on this topic you should consult the Excel Help.