I am hoping that a learned mind on this forum can assist me with the following text formula query.

I am using an add-on to MS Project that requires me to create a text field and populate it with data in the following format (numeric examples given);

123456:345678
Startchainage:Endchainage

I currently have 2 number fields in MS Project as follows;
Start Chainage = custom number field [NUM1];
Finish Chainage = custom number field [NUM2];

I have tried create a custom text field formula and Concatenate using [num1]&":"&[num2] but this produced a #error response.

Does anyone have any advice regarding how I can Concatenate [num1] & [num2] and insert a colon":" in the middle to produce Startchainage:Endchainage in a text field?

Best Regards and My Thanks in Advance

Jason